The deferred income tax balance sheet accounts arise from temporary differences between the amount of assets and liabilities recognized for financial reporting and tax purposes.
Components of the deferred tax assets and liabilities at December 31 were as follows:
[1] Upon adoption of ASC 842, deferred taxes associated with previously recognized deferred rent liabilities were reclassified into deferred taxes for ROU asset and lease liability.
As of December 31, 2019, the Company had approximately $19.0 of tax-effected U.S. federal net operating loss carryforwards. Some of these net operating loss carryforwards have an indefinite carryforward period, and those that do not will begin to expire in 2021 if not utilized. The majority of the U.S. federal net operating loss carryforwards are subject to limitation under the Internal Revenue Code of 1986, as amended (“IRC”) Section 382; however, the Company expects to utilize such losses in their entirety prior to expiration. The U.S. federal net operating loss carryforwards decreased from 2018 to 2019 primarily due to current year tilization. The Company has approximately $33.7 of tax-effected state net operating loss carryforwards (without regard to federal benefit of state). Some of these net operating loss carryforwards have an indefinite carryforward period, and those that do not will begin to expire in 2020 if not utilized. The state net operating loss carryforwards are primarily related to Florida and New Jersey, but the Company has smaller net operating losses in various other states. The Company has approximately $65.6 of tax-effected foreign net operating loss carryforwards. Some of these net operating loss carryforwards have an indefinite carryforward period, and those that do not will begin to expire in 2020 if not utilized. The foreign net operating loss carryforwards increased from 2018 to 2019 primarily due to the recognition of a discrete tax benefit of $41.0 in connection with a foreign restructuring plan allowing the future realization of net operating losses. Additionally, the Company has $5.0 of U.S. federal and state research and develop- ment tax credit carryforwards (without regard to federal benefit of state). Some of these research and development credit carry- forwards have an indefinite carryforward period, and those that do not will begin to expire in 2020 if not utilized.
As of December 31, 2019, the Company determined that a total valuation allowance of $36.3 was necessary to reduce U.S. fed- eral and state deferred tax assets by $15.4 and foreign deferred tax assets by $20.9, where it was more likely than not that all of such deferred tax assets will not be realized. As of December 31, 2019, the Company believes it is more likely than not that the remaining net deferred tax assets will be realized based on the Company’s estimates of future taxable income and any applicable tax-planning strategies within various tax jurisdictions.
Table:
 | 2019 | 2018
Deferred tax assets: |  | 
Reserves and accrued expenses | $    175.2 | $    156.5
Inventories | 4.3 | 4.5
Net operating loss carryforwards | 111.2 | 67.9
R&D credits | 4.1 | 6.1
Valuation allowance | (36.3) | (26.4)
Outside basis difference on investments held for sale | — | 2.7
Lease liability1 | 64.0 | —
Total deferred tax assets | $    322.5 | $    211.3
Deferred tax liabilities: |  | 
Reserves and accrued expenses | $      15.5 | $      14.3
Amortizable intangible assets | 1,229.9 | 1,043.0
Plant and equipment | 10.8 | 6.6
Accrued tax on unremitted foreign earnings | 17.1 | 16.3
Outside basis difference on investments held for sale | — | 10.0
ROU asset1 | 61.7 | —
Total deferred tax liabilities | $ 1,335.0 | $ 1,090.2


Question: How do the deferred income tax balance sheet accounts arise from?
Answer: temporary differences between the amount of assets and liabilities recognized for financial reporting and tax purposes