The rail industry was one of the first to pioneer private pensions for its employees in the late 19th century, and by the 1930s, these pensions were more developed than in most other industries. However, according to RRB, these private rail pensions had serious defects that were magnified by the effects of the Great Depression. For instance, RRB noted that the plans were generally inadequately financed and that employers could terminate the plans at will. In prior work, we noted that the Railroad Retirement Act of 1937 was enacted at the urging of rail labor and established the national railroad retirement system administered by RRB. The program was to be solely supported by employees and employers of the rail industry through payroll taxes. According to RRB, this system was created separately from Social Security for several reasons. For instance, RRB notes that Social Security—created in 1935—would not begin payments for several years or credit workers for work prior to 1937, while the deteriorating state of private rail pensions called for immediate retirement payments based on prior service. We previously reported that the 1951 amendments to the Railroad Retirement Act of 1937 substantially increased railroad retirement benefits to bring them in line with benefit increases granted to individuals under Social Security, and that a financial interchange was created between the agencies in 1951 to help pay for these increases. RRB annually computes the amounts that SSA would have collected in taxes from rail workers and their employers, and what SSA would have paid in benefits if rail workers had been covered under Social Security, with the net difference transferred between the agencies. The amounts computed under the financial interchange do not necessarily represent the actual RRB benefits paid to rail workers and their beneficiaries. RRB determined that it was due a net transfer from SSA each year since 1958. Financial interchange transfers make up a significant portion of the financing for RRB’s retirement, disability, and survivors benefits. In fiscal year 2016, RRB paid about $12.4 billion in these benefits and collected $5.9 billion in payroll taxes from rail employees and employers. RRB reported that the remainder of its funding for these benefits came from the financial interchange ($4.1 billion), transfers from the National Railroad Retirement Investment Trust ($1.4 billion), income taxes collected on RRB benefits ($758 million), and other funding sources, such as appropriations. The interchange also serves as a vehicle to fund Medicare Part A (Hospital Insurance) benefits for rail workers. The benefits provided by RRB consist of a core-level of benefits that are similar to those available to most workers covered under Social Security, including Medicare. Rail workers also receive a second level of retirement benefits that approximate payments from private pension plans (see table 1). For non-rail workers, Social Security and Medicare benefits are paid from their respective trust funds: Retirement benefits are paid from SSA’s OASI Trust Fund; Disability benefits are paid from SSA’s DI Trust Fund; and Medicare Part A benefits are paid from the Hospital Insurance Trust Fund. The financial interchange is intended to place Social Security’s OASI and DI Trust Funds and HHS’s Hospital Insurance Trust Fund on the same financial footing as if rail workers and beneficiaries were covered under Social Security instead of by RRB. Regarding Social Security, RRB is credited for what it paid beneficiaries, administrative costs involved with paying benefits, and interest for the time between the determination of the interchange amount and its actual transfer. SSA is credited for the amount of payroll and income taxes it would have collected from rail workers and for income taxes that would have been paid by RRB beneficiaries on Social Security equivalent benefits. The net of the five amounts is the amount that is transferred (see fig. 1). A net transfer from SSA to RRB means that rail workers would have been a net draw on SSA’s trust funds if covered under Social Security. RRB calculates the financial interchange amount each year, which is done on a retrospective basis, i.e., the amount is determined for the previous fiscal year. By law, the agencies must complete their determination by June of each year. In keeping with the purpose of keeping the OASI and DI trust funds in the same place as if rail workers were covered under Social Security, RRB determines the retirement and disability benefits that rail workers and dependents would have received if they were covered under Social Security. Specifically, RRB uses railroad earnings data provided by employers to replicate SSA’s benefits calculations. Although the basic retirement and disability benefits that SSA and RRB pay to their beneficiaries are based on the same formulas, there are several eligibility differences between the two programs. For instance, a rail worker may receive unreduced retirement benefits at age 60 after 30 years of work, whereas the earliest most workers covered under Social Security can begin receiving retirement benefits is at age 62. According to RRB officials, even though a 60-year-old railroad worker may be receiving RRB retirement benefits, RRB would not receive credit through the interchange for that individual. Once that individual turns 62, RRB determines the amount of reduced Social Security retirement benefits for which he or she would have been eligible, given the person’s earnings history and Social Security’s benefits rules. According to RRB officials, the agency receives a credit through the interchange for this amount even though the individual is receiving full RRB retirement benefits. To account for these potential differences, RRB officials said that the agency must make calculations for individual RRB cases. Additionally, RRB officials said that in light of the number of RRB cases—nearly 400,000—it is not practical to make these calculations annually for each case. Instead, RRB uses SSA rules to calculate benefits for a subset of RRB cases in which the worker’s Social Security number ends in 30, which approximates a 1-percent sample. The sample size was about 4,000 for fiscal year 2016. Once RRB completes its benefit calculation for each of those cases, it aggregates the result and produces an estimated amount for its entire population of cases (see fig. 2). RRB reported in its annual financial interchange determination report that it was credited $7.2 billion dollars in fiscal year 2016 for the estimated amount beneficiaries would have been paid under Social Security. These expenses represent those that SSA would have incurred to administer benefits had rail workers been covered under Social Security (as opposed to the actual amount RRB spent to administer its programs). These expenses, which SSA would have funded out of its trust funds, include the cost to enroll individuals in its programs and maintain its benefit rolls. RRB calculates the amount of administrative expenses based on unit-cost data provided by SSA. RRB reported that it was credited about $22 million in administrative costs for fiscal year 2016. SSA credits RRB for interest that accrues on the annual financial interchange transfer from the period in time for which it is calculated (the end of the fiscal year on September 30) until the amount is transferred to RRB in June of each year. The interest rates are equal to those SSA earns on its trust funds. RRB reported that it was credited about $163 million in interest for fiscal year 2016. This amount represents the payroll taxes rail employees and employers would have paid into Social Security’s trust funds had workers been covered under Social Security. SSA and RRB generally levy payroll taxes on earnings at the same rate, and RRB officials told us they use payroll data from employers to determine this amount. RRB reported that it credited SSA $2.4 billion for fiscal year 2016. Some RRB beneficiaries pay income taxes on the benefits they receive, and that tax revenue is credited to SSA’s trust funds through the financial interchange. To put the OASI and DI trust funds in the same place as if rail workers were covered under Social Security, RRB credits SSA for the amount of income tax railroad beneficiaries paid on Social Security equivalent benefits. RRB computes this amount using tax data from the Department of the Treasury, and credited about $296 million to SSA for fiscal year 2016. RRB also may adjust calculations on transfers from prior years; for instance, if new income was reported for individuals or if benefit overpayments are discovered for individuals in the sample. The process for determining the financial interchange transfer with HHS— which helps finance Medicare benefits for rail workers—has fewer components than for retirement and disability benefits. Generally, RRB determines the Medicare payroll taxes and income taxes paid by rail workers and transfers this amount, less administrative expenses, to HHS (see fig. 3). RRB estimates how much it collects in Medicare payroll taxes by using payroll data provided by employers for workers whose Social Security numbers end in 30. RRB credited HHS for about $637 million for fiscal year 2016. Overall, the procedures we observed, and which RRB explained and demonstrated, for calculating the financial interchange are consistent with the methodology agreed to by RRB, SSA, and HHS. An annual determination report produced by the three agencies documents this methodology. Additionally, several audits conducted for the RRB Office of Inspector General determined that the methodology is appropriate for achieving the purpose of the financial interchange. Specifically, the audits concluded that the sample used in calculating benefits was representative of RRB’s population of beneficiaries, the formulas used to project the results of the sample on the entire population of beneficiaries were consistent with RRB’s design, and that assumptions made by RRB when carrying out calculations were reasonable. SSA has made a net transfer to RRB through the financial interchange each year since 1958. The cumulative net transfer from the Social Security trust funds to RRB through 2015 was approximately $266 billion in 2016 dollars. Of this amount, transfers related to retirement and survivor benefits comprised about $256 billion and disability benefits accounted for about $10 billion. This trend in transfers is primarily caused by RRB benefit payments exceeding payroll taxes collected as calculated by the interchange, which has been the case each year of the financial interchange, resulting in a net amount owed to RRB from SSA each year (see fig. 4). Based on the data RRB reported, the continuing flow of funds to RRB from SSA has largely been driven by a steadily shrinking number of active workers in the rail industry paying payroll taxes in support of a larger population of beneficiaries. According to RRB data, the number of workers in the rail industry peaked at the end of World War II, when there were almost 1.7 million workers. Since then, this number declined steadily to about 231,000 in 2016. Additionally, the number of beneficiaries has exceeded the number of active workers since 1961. According to RRB data, there was about 1 beneficiary for every 10 workers in 1938; the ratio had increased to 3 beneficiaries for every 10 rail workers in 1951, when the financial interchange was created. By 2016, there were 28 beneficiaries for every 10 workers. Furthermore, RRB officials noted that another factor causing increased fund transfers from SSA to RRB was a series of successive amendments to the Social Security Act which raised benefits immediately while deferring tax increases to pay for the increased benefits. As a result of these two factors, the payroll taxes paid by rail workers have not been sufficient to pay for all of the benefits paid by RRB. Hence, the financial interchange has consistently transferred money from SSA to RRB (see fig 5). According to SSA actuarial estimates, the flow of funds to RRB from SSA is projected to continue. Social Security’s 2017 trustees report projects that the amount of transfers to RRB will continue to grow though at least 2026. Moreover, RRB’s most recent actuarial valuation report estimates that under three employment assumptions—optimistic, moderate, and pessimistic—the number of beneficiaries will continue to exceed the number of rail workers through at least 2088. RRB has collected payroll taxes for HHS since 1966. From 1966 through 2016, RRB reported that it transferred a total of $30 billion in 2016 dollars through the financial interchange to the Hospital Insurance Trust Fund (see fig. 6). RRB takes a number of steps to ensure that the financial interchange amount is accurately calculated each year. For example: Sample verification: To make sure that the financial interchange sample is up to date, RRB staff told us that they query their beneficiary database at the beginning and end of the annual financial interchange calculation to ensure that all beneficiaries who should be part of its sample—those with a Social Security number ending in 30—are included. Those included in the sample can change from year to year, for instance, when new beneficiaries join the retirement rolls or when beneficiaries die. Supervisory review: RRB officials told us that the work of a new employee who calculates the financial interchange is reviewed by another employee until the new employee is determined to be proficient. Error checks: Electronic error checks built into the system RRB uses to calculate the financial interchange help prevent mistakes by flagging erroneous values. These checks alert employees in real time that an incorrect value may have been entered (for example, a benefit amount that exceeds what beneficiaries can receive). Officials also told us that they run similar checks in batches throughout the year to sweep for any potential errors that were not addressed by employees. They noted that they will work with staff to address all potential errors before the financial interchange calculation is finalized. However, RRB’s error checks do not cover all potential erroneous values. High-level review: RRB officials told us that the Chief of Benefit and Employment Analysis and his staff review the results of the interchange calculations and determine if the end result is reasonable compared to projections made earlier in the year, based on actual payroll and beneficiary data. Despite these steps, limitations in RRB’s error checks and its reliance on manual data entry are potential sources of mistakes in financial interchange calculations. The process RRB staff follow in computing benefit amounts for the financial interchange involves manual data entry of earnings data and SSA-equivalent benefits. RRB’s error checks will help identify values that are impossible—such as a benefit amount that exceeds the maximum a beneficiary can receive—but not values that are incorrect but still within the range of possibility. RRB staff demonstrated this scenario for us and acknowledged this as a limitation in their internal controls. Any data entry errors have the potential to result in larger errors in the financial interchange determination. The benefits portion of the financial interchange determination is based on a sample of all cases. Should any errors occur in the sample, they will be magnified when RRB inflates the estimate to arrive at an amount for the entire population of beneficiaries. Additionally, RRB’s process could result in incorrect transfers for years. The sample is chosen in the same way each year—individuals with Social Security numbers ending in 30—so the same cases will remain part of the sample until the individuals leave the rolls. RRB officials told us that they generally only have to do a full set of calculations for new cases or cases in which additional income is detected that affects benefit amounts. RRB officials estimated that about 20 percent of cases in the financial interchange sample each year require a full calculation. For the remainder of cases in the interchange sample, officials said that no annual recomputation is needed. Instead, the previous year’s results are adjusted according to any cost of living increase. If a data entry error is made in one of these cases, RRB may not discover it until the individual leaves the rolls or dies, at which point RRB staff told us they recalculate the individual’s benefit amount. Data sharing between RRB and SSA could reduce the potential for data entry errors, but the two agencies have not recently pursued this option. RRB officials told us that prior to 2008 they used computer code to automatically save data from SSA databases into spreadsheets, where the data could be used for calculating the financial interchange. However, SSA instructed RRB to stop using this method in 2008 because of security concerns about saving this information outside of SSA systems. RRB officials added that this constraint prevents them from developing a more efficient method of data collection that would improve the accuracy and timeliness of benefit calculations for the financial interchange. However, RRB officials said that they have not formally approached SSA in the last several years to discuss potential alternatives for gaining greater access to data. SSA officials said that RRB should follow SSA’s procedures for requesting a data exchange if RRB wishes to revisit this topic. Federal internal control standards state that agencies should use quality information to achieve their objectives. By taking additional steps to obtain data from SSA electronically, RRB can better position itself to ensure that data entered into its systems are correct and that its calculations are free of errors. RRB has limited documentation and does not have formal policies to guide several key aspects of the financial interchange calculation. While we did not identify any actual errors in its calculations, these shortcomings in its controls increase the risk of calculations being carried out inconsistently or incorrectly. The broad steps that RRB takes to determine the amounts of the financial interchange are documented in an annual determination report produced by RRB. They include, for example, the factors used to calculate administrative costs, discussion of adjustments made to calculations from prior years, and descriptions of the formulas used to project the results of RRB’s benefit sample to the population of railroad beneficiaries. However, the agency does not have clear documentation of the detailed steps used by staff to calculate the interchange amounts. A 2010 audit of the financial interchange process conducted for the RRB Office of Inspector General found that documentation of the financial interchange process was insufficient for a knowledgeable third party to replicate without verbal explanation from RRB staff. In response, RRB officials told us that they produced some documentation such as charts showing the workflows for different portions of the process, such as for calculating benefits, payroll taxes, and financial projection—and instructions for staff in RRB’s Bureau of the Actuary for high-level review of the formulas and entries for the final calculation results. However, the documentation did not provide enough detail about the steps staff must take when conducting financial interchange calculations so the process can be followed without additional explanation. For instance, the documentation did not discuss the process by which staff obtain earnings data and enter it into SSA’s benefit calculator, manually enter the results into RRB’s system, or the different alerts that notify staff of potential mistakes and how staff deal with them. Federal internal control standards state that effective documentation provides a means to retain organizational knowledge and mitigate the risk of having knowledge limited to a few personnel, as well as a means to communicate that knowledge as needed to external parities, such as auditors. Written documentation with specific steps for carrying out the financial interchange calculation and using its data system would help RRB ensure that its staff and others could carry out and replicate its process consistently. RRB does not have current or complete documentation related to the computer system it uses to compute the financial interchange. Specifically, RRB officials said that they do not have current documentation such as a manual or data dictionary that would provide information on the data elements in the system, their definitions, descriptions, and range of potential values. They said a data dictionary is not necessary because data are contained in a format in which rows and columns are labeled according to fields and years. However, such labeling does not include documentation, for example, about whether values entered in those fields are allowable. Federal internal control standards state that effective documentation is needed to retain knowledge and prevent knowledge from being limited to a few staff. Even if the data system is relatively uncomplicated, without such documentation, it is difficult for RRB staff and others to fully understand all elements in the system, and it could complicate efforts to make any changes in the future or bring new staff up to speed on the system. RRB does not have written procedures for how to address instances in which staff do not correct potential errors flagged by its computer system. As noted earlier, RRB’s system for calculating the financial interchange will alert staff to potential data entry errors. RRB officials said this system has the ability to allow staff to override the alert in some cases, generally in complex cases, such as when RRB benefits are offset by other public pensions. In these cases, the system does not distinguish between an actual error and instances in which additional work and review are needed because of complex benefit calculations. Staff can override the alert in these cases where there is no actual error, but officials noted that a report of potential errors that is generated by the system would still include these cases, which may be referred back to staff for clarification or correction. If implemented correctly, these procedures could help staff take appropriate action on these complex cases. However, current procedures are not formally documented and officials said they have not considered producing written procedures because they believe the process for addressing alerts is clear. Federal internal control standards indicate that effective documentation assists in management’s design of internal controls and can mitigate the risk that knowledge is limited to a few staff. RRB’s lack of written procedures can make it difficult for staff or reviewers to know if procedures are carried out consistently—such as whether staff appropriately override an error alert—and can create challenges if there is staff turnover. It is important to ensure that all potential errors are addressed correctly given that mistakes in the financial interchange sample can be multiplied when estimating benefit payments for the universe of RRB beneficiaries. According to RRB officials, new employees will have their calculations reviewed until the employees are deemed to be proficient, and calculations by any staff member are subject to review and periodically reviewed for accuracy. Federal internal control standards call for documenting agency procedures. However, RRB does not have a minimum or maximum time established for which it will review the work of new staff, and does not have an overall policy for reviewing staff members’ work after they have been deemed proficient. Officials told us they had not considered setting a policy regarding supervisory review. They added that individualized, on-the-job training is more appropriate for new staff than a formalized process. In the case of current employees, any potential errors would be identified when the case is terminated, at which time all cases are reviewed and recomputed. Additionally, officials said that a formal policy would not increase the number of cases reviewed and potentially constrain their ability to correct new errors as they occur. Nonetheless, without formal policies on supervisory review, RRB cannot reasonably ensure that the work performed by staff is adequately or consistently reviewed for quality. SSA and HHS provide some oversight of the financial interchange process, but do not review case-level calculations. Both agencies approve the results of the financial interchange calculations, but officials from SSA and HHS told us that their oversight is limited to high-level reviews of RRB’s calculations to determine whether results significantly vary from previous years. For instance, staff from SSA’s Office of the Chief Actuary told us that they examine RRB’s payments and revenues against SSA’s benefits paid and payroll taxes collected to determine if there are large or inexplicable changes from year to year, in which case they will ask RRB for additional information to understand the changes. Additionally, RRB officials told us that formulas used in their spreadsheets to calculate the results of the interchange have been reviewed by SSA actuaries. While these actions could help identify larger errors, the agencies will not be able to detect whether errors are made on complex, case-level calculations or if SSA rules are being correctly followed. In response to prior errors in financial interchange calculations, RRB officials told us that SSA reviewed case-level calculations from the 1990s until 2002. SSA officials told us that they have not reviewed cases since then because of resource constraints. A 2009 SSA Office of the Inspector General report recommended that the agency consider increasing its oversight of the process, such as setting a schedule for review of individual cases given the importance of reviews in verifying transfers. However, SSA has not taken action on this recommendation. HHS officials told us that the financial interchange is one of a number of relatively small funding streams and the agency has never had cause to suspect mistakes and has never examined case-level calculations. Federal internal control standards state that agencies should establish and operate monitoring activities to evaluate the results of activities. Without monitoring how calculations are made, SSA cannot reasonably ensure that the transfers it makes or receives with RRB are accurate. In commenting on a draft of this report, HHS raised questions about whether it has the authority to review case-level calculations, but noted in follow-up communication that this issue is currently undergoing legal review at HHS. As a result, HHS officials told us that they would not be able to provide additional clarification at this time. We continue to believe that HHS would be better positioned to ensure that transfers it makes and receives are calculated correctly if it reviews case-level calculations. The financial interchange provides RRB with a significant portion of its funding, and trends in the number of beneficiaries and workers suggest this will continue to be the case in the future. RRB developed a process to calculate the financial interchange amount, and the accuracy of the calculations depends in large part on correct data being manually entered into RRB’s computer system. However, RRB’s current controls do not address some potential sources of error. Having the ability to electronically obtain data from SSA could help reduce the risk posed by data entry errors. Further, RRB has limited written documentation for carrying out aspects of the financial interchange calculation, such as how its computer system is structured, how to address instances when staff override error alerts, and how staff work is reviewed. Without such documentation, RRB puts itself at risk of staff carrying out actions inconsistently, losing operational knowledge when staff leave or retire, and complicating oversight of its operations. Lastly, SSA and HHS increase the risk of errors by not performing case- level reviews of financial interchange calculations. This is especially true for the SSA portion of the interchange, which involves complex calculations performed according to SSA rules. In its role as the administrator of the OASI and DI programs, SSA is best positioned to determine if its rules are properly being applied to financial interchange calculations. The large sums SSA transfers through the interchange— over $4 billion annually—warrant additional oversight to ensure that transfer amounts are correct. We are making a total of eight recommendations, including five to RRB (The Board), two to the Commissioner of SSA, and one to the Secretary of HHS. The Board should work with SSA to explore options for obtaining data electronically and limiting the reliance of the financial interchange process on manual data entry. (Recommendation 1) The Board should produce written documentation on the financial interchange process such that a knowledgeable third party could carry out and replicate its process consistently without further explanation. (Recommendation 2) The Board should produce written documentation of its computer system and its structure, such as a manual for the computer system, and data dictionary to provide information on the data elements in the system, their definitions, descriptions, and range of potential values. (Recommendation 3) The Board should produce written documentation of its procedures for instances when staff override error alerts generated by its computer system. (Recommendation 4) The Board should produce formal policies on how the work of staff performing the financial interchange is reviewed. (Recommendation 5) The Commissioner of SSA should work with RRB to explore options for electronically sharing data and limiting the reliance of the financial interchange process on manual data entry. (Recommendation 6) The Commissioner of SSA should take additional steps to provide oversight of financial interchange calculations at the individual-case level. This could include periodically reviewing a subset of these cases. (Recommendation 7) The Secretary of HHS should, consistent with its existing statutory authority, take additional steps to provide oversight of financial interchange calculations at the individual-case level. If the Secretary concludes that there are limitations in its authority in this area, the Secretary should seek to obtain the necessary additional authority. (Recommendation 8) We provided a draft of this report to RRB, SSA, and HHS for review and comment. In written comments, both RRB and SSA agreed with the recommendations. RRB noted that it will devote the resources needed to improve the written documentation of its procedures and computer system. RRB and SSA also provided technical comments which we incorporated as appropriate. Copies of their written comments are reproduced in appendixes I and II. In written comments, which are reproduced in appendix III, HHS disagreed with the recommendation that it take additional steps to provide oversight of financial interchange calculations at the individual-case level. HHS noted that while in theory it may be a good idea to incorporate such review into the process, it is limited by statute in its ability to oversee how RRB calculates transfers between HHS and RRB. HHS went on to describe a section of the Social Security Act that they noted “pertains more to Supplemental Medical Insurance trust fund draws for administrative costs.” Notably, with respect to HHS, our report does not involve that trust fund, but rather addresses the Hospital Insurance Trust Fund. Although HHS’s comments did not clarify why it believes that this section of law would limit its authority with respect to the Hospital Insurance Trust Fund, it nevertheless asserted that it does apply in this scenario. We reached out to HHS to seek clarification of its comments. For example, we inquired about the applicability of a separate provision of law that would appear to establish a role for HHS to work with RRB to determine financial interchange amounts. Ultimately, HHS did not provide the clarification we sought, instead indicating via email that this recommendation is currently undergoing legal review and that HHS is unable to provide a response to our questions at this time. HHS further stated that it will continue to work on this issue to provide GAO with updates in the future. In light of the uncertainty surrounding HHS’s authority in this area and the fact that HHS declined to respond to our requests for clarification of its legal authority, we have modified our recommendation to reflect the fact that HHS may need to seek additional statutory authority to implement our recommendation, should HHS determine it to be necessary. As agreed with your offices, unless you publicly announce the contents of this report earlier, we plan no further distribution until 30 days from the report date. At that time, we will send copies of this report to the appropriate congressional committees, the Railroad Retirement Board, the Commissioner of the Social Security Administration, and the Secretary of the Department of Health and Human Services. In addition, the report will be available at no charge on the GAO website at http://www.gao.gov. If you or your staff have any questions, please contact me at (202) 512- 7215 or curdae@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. GAO staff who made significant contributions to this report are listed in Appendix IV. In addition to the contact named above, Mark Glickman (Assistant Director), Daniel R. Concepcion (Analyst-in-Charge), and Randy DeLeon made key contributions to this report. Additional contributors include David Ballard, Carl Barden, William Boutboul, James Cosgrove, Alexander Galuten, Jennifer Gregory, Sheila McCoy, Jean McSween, Mimi Nguyen, Joseph Silvestri, Almeta Spencer, and Kate van Gelder.

Summary: RRB collects payroll taxes and administers retirement, disability, and Medicare benefits for rail workers and their families. A financial interchange exists between RRB, SSA, and HHS in order to put the trust funds for these benefits in the same financial position as if Social Security covered rail workers. RRB generally transfers to the Social Security and Hospital Insurance trust funds the taxes that would be collected from rail workers and employers, while SSA provides RRB the benefits that would otherwise be paid directly to rail workers. GAO was asked to review the financial interchange calculation process. This report examines (1) the steps taken to calculate financial interchange amounts, (2) factors that could account for trends in transfers over time, and (3) the extent to which RRB, SSA, and HHS provide oversight to ensure calculations are accurate. GAO reviewed agency policies, procedures, and regulations; observed RRB staff calculating four cases selected for beneficiary type; reviewed data on payment and beneficiary trends; and interviewed agency officials. Established in 1937, the Railroad Retirement Board (RRB) administers retirement and disability benefits for rail workers and their families. A financial interchange between RRB and the Social Security Administration (SSA) was created in 1951, which as GAO previously reported, helped finance RRB benefits as they increased over time to keep pace with growing Social Security benefits to individuals. Through its financial interchange calculation, RRB takes steps each year to estimate the amount of funds that would have flowed in and out of Social Security's trust funds if rail beneficiaries were covered by Social Security instead of RRB. Five key steps go into the annual calculation: RRB is credited for (1) the estimated amount of benefits it would have paid to beneficiaries under SSA rules, (2) administrative costs, and (3) interest accrued on the financial interchange amount. SSA is credited for the revenues it would have received from rail workers if they paid into Social Security; specifically, (4) payroll taxes and (5) income taxes paid on benefits received. The determined net amounts are transferred between the agencies, which since 1958 have been from SSA to RRB each year. RRB received $4.1 billion in fiscal year 2016, almost one-third of the $12.4 billion in retirement and disability benefits it paid that year. The financial interchange was expanded to Medicare in 1965 to facilitate funding of Medicare benefits to rail workers; RRB transfers Medicare payroll taxes collected, income taxes paid on benefits received, and interest, minus administrative costs to the Department of Health and Human Services (HHS). A high ratio of beneficiaries to active railroad workers primarily explains the net transfers from Social Security's trust funds to RRB each year since 1958. Rail employment has fallen steadily since World War II, and the number of beneficiaries has exceeded the number of workers since 1961. RRB had 2.7 beneficiaries for every worker in 2015. As a result, RRB has paid out more in benefits than it has collected in payroll taxes and projects this to continue for the foreseeable future. RRB takes a number of steps each year to ensure the accuracy of its calculations, such as checking that the sample of cases used to estimate benefit payments is complete, reviewing the work of new employees, and using electronic alerts to help prevent staff from entering incorrect information into its computer system. SSA and HHS also conduct high-level reviews of the calculation results to identify any significant changes from one year to the next. However, RRB's process includes manual data entry and its electronic edit checks cannot flag entries that are incorrect but plausible, which could lead to calculation errors. RRB also has limited documentation of its calculation process, and does not have formal policies on how staff should address some potential calculation errors and on how supervisors should review staff work. This is contrary to internal control standards for having quality data and documenting procedures. In terms of SSA and HHS, they do not currently review case-level calculations made by RRB, and cannot reasonably ensure that work used to determine the transfers they made and received is correct. GAO makes eight recommendations, including that RRB create formal policies and improve documentation of its processes, work with SSA to obtain data electronically, and that SSA and HHS increase their oversight. RRB and SSA agreed, while HHS did not, asserting that statute limits its authority; however, HHS continues to review this issue. HHS should seek this authority if it determines it necessary.