The Supplemental Nutrition Assistance Program (SNAP), formerly called the Food Stamp Program, is designed primarily to increase the food purchasing power of eligible low-income households to a point where they can buy a nutritionally adequate low-cost diet. This report describes the rules related to eligibility for SNAP benefits and the rules related to the issuance and use of benefits. SNAP is authorized by the Food and Nutrition Act of 2008. This law, formerly the Food Stamp Act of 1977, has since 1973 been reauthorized by the "farm bill," omnibus legislation that also typically includes the reauthorization of other federal agricultural policies and programs. SNAP was most recently authorized by the 2014 farm bill (Agricultural Act of 2014; P.L. 113-79 ). See CRS Report R43332, SNAP and Related Nutrition Provisions of the 2014 Farm Bill (P.L. 113-79) for further discussion of the nutrition program policy changes. The Food, Conservation, and Energy Act of 2008 ("2008 farm bill," P.L. 110-246 ) changed the name of the program from the Food Stamp Program to SNAP and revised the name of the governing law from the Food Stamp Act to the Food and Nutrition Act. State names for the program may vary; some states continue to name their programs "food stamps," while others have switched to SNAP or maintain another name. The U.S. Department of Agriculture's Food and Nutrition Service (USDA-FNS) administers SNAP. Although a detailed framework of federal law and regulation exists, a robust framework of state options and waivers exists as well. In this way, while universal concepts of benefit eligibility and administration exist among the states, there also are many policies that vary among the states. This report will focus on the federal framework but will at times discuss state options that may cause state and local programs to vary. SNAP benefits are available for households that meet federal financial eligibility tests for limited monthly income and liquid assets. However, these rules can be bypassed through the use of "categorical eligibility" for SNAP. Categorical eligibility provides states with the ability to modify federal financial eligibility rules. As of February 2018, 42 states utilize broad-based categorical eligibility, although several do so with an added limit on liquid assets. To be eligible for SNAP, a household must fulfill requirements related to work effort and must meet citizenship and legal permanent residence tests. In general, the maximum SNAP benefit is based upon the level of the U.S. Department of Agriculture's lowest cost food plan (the Thrifty Food Plan or TFP) and varies by household size. Monthly SNAP benefit amounts are calculated as the difference between the household's expected contribution to its food costs and the maximum benefit. (Participating households are expected to devote 30% of their "net" monthly cash income to food purchases.) Thus, a recipient household with no "net" cash income receives the maximum monthly SNAP allotment for its size while a household with some counted income receives a lesser allotment, the maximum benefit minus 30% of the net income. Net income is the gross income with certain specified deductions subtracted. Throughout the body of this report, current participation, benefit amount, and spending figures are provided. For a historical table of such information (dating back to 1985), see Table A-1 . SNAP has financial, work-related, and "categorical" tests for eligibility. Its financial tests require that those eligible have monthly income and liquid assets below limits set by law and adjusted for inflation. Under the work-related tests, certain household members must register for work, accept suitable job offers, and fulfill work or training requirements (such as looking or training for a job) established by their state public assistance agency. Under a time limit established in 1996, SNAP eligibility for Able-bodied Adults Without Dependents (ABAWDs) is limited to 3 months in any 36-month period unless the ABAWD works at least half time or is in a work or training program. Categorical eligibility rules make some automatically eligible for SNAP assistance (most who receive a benefit from the Temporary Assistance for Needy Families [TANF] block grant or receive Supplemental Security Income [SSI] or state [GA] cash benefits). In addition to categorical eligibility rules, there are also categorical denials of eligibility to specific groups (e.g., strikers, many noncitizens and postsecondary students, people living in institutional settings, many drug felons). However, applications cannot be denied because of the length of a household's residence in a SNAP agency's jurisdiction, because the household has no fixed mailing address or does not reside in a permanent dwelling, or because the applicant does not provide a driver's license or photograph identification. The basic SNAP beneficiary unit is the household. A household can be either a person living alone or a group of individuals living together; there is no requirement for cooking facilities. The SNAP household definition is different than that used in other means-tested programs (e.g., TANF families with dependent children, elderly (60 years or older) or disabled individuals or couples in the SSI Program). However, it is close to those used by some other programs such as the National School Lunch Program; the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC); and the Low-Income Home Energy Assistance Program (LIHEAP). Generally speaking, individuals living together constitute a single household if they customarily purchase food and prepare meals together. Members of the same household must apply together, and their income, expenses, and assets normally are aggregated in determining food stamp eligibility and benefits. However, persons who live together can sometimes be considered separate "households" for program purposes. Persons who live together, but purchase food and prepare meals separately, may apply for SNAP benefits separately, except for (1) spouses; (2) parents and their children (21 years or younger); and (3) minors 18 years or younger who live under the parental control of a caretaker (excluding foster children and, in some cases, certain citizen children, who may be treated separately). In addition, persons 60 years or older who live with others and cannot purchase food and prepare meals separately because of a substantial disability may apply separately from their co-residents as long as their co-residents' income is below prescribed limits (165% of the federal poverty guidelines). Although those living in institutional settings generally are barred from SNAP, individuals in certain types of group living arrangements may be eligible and are automatically treated as separate households, regardless of how food is purchased and meals are prepared. These arrangements must be approved by state or local agencies and include residential drug addiction or alcoholic treatment programs, small group homes for the disabled, shelters for battered women and children, and shelters for the homeless. If a household includes an elderly or disabled member, the household is entitled to different SNAP deduction rules as well as some different financial eligibility rules (discussed in the next section). Financially eligible one- and two-person households (in the 48 contiguous states and DC) are also assured (for FY2018) a minimum monthly benefit of $15. Without the minimum benefit it may be possible that these smaller households would be eligible for SNAP but for an arguably negligible amount. It is possible that different SNAP households can live together, and recipients can reside with non-recipients. In the case of recipients residing with non-recipients, the eligibility and benefit level of the household is based on a household size that excludes the non-recipient. Whether the non-recipient's income or assets are included depends upon the specific circumstances. There are two pathways to eligibility for SNAP. The first is the "traditional pathway" to eligibility with financial eligibility thresholds stated in the Food and Nutrition Act (7 U.S.C. 2011 et seq.). Federal law sets income and asset eligibility thresholds as well as the rules for what types of income and assets are counted or disregarded. Also, the act lists what types of expenses can be deducted in determining income eligibility and, if eligible, determining the benefit amount. The second pathway is known as "categorical eligibility." The basis of categorical eligibility is a rule that makes households composed entirely of recipients of benefits funded from the Temporary Assistance for Needy Families (TANF) block grant, Supplemental Security Income cash assistance, or state General Assistance (GA) automatically eligible for SNAP. Recipients of benefits from these programs bypass financial eligibility rules and automatically go to the next step, determining SNAP benefits. However, states have the option of interpreting categorical eligibility broadly. Below is a discussion of the traditional pathway to SNAP eligibility, followed by a discussion of categorical eligibility. For households without an elderly or disabled member, SNAP uses both the household's basic (or "gross") monthly income and its counted (or "net") monthly income. Eligible households' gross income must be at or below gross income standards and their counted income must meet net income eligibility thresholds. When judging eligibility for households with elderly or disabled members, only the household's counted net monthly income is considered; in effect, this procedure applies a somewhat more liberal income test to the elderly and disabled.