Significant components of Autodesk’s deferred tax assets and liabilities are as follows
Autodesk’s tax expense is primarily driven by tax expense in foreign locations, withholding taxes on payments made to the U.S. from foreign sources, and tax amortization on indefinite-lived intangibles offset by a tax benefit resulting from release of uncertain tax positions upon finalization of IRS examination and release of valuation allowance from acquired deferred tax liabilities.
Autodesk regularly assesses the need for a valuation allowance against its deferred tax assets. In making that assessment, Autodesk considers both positive and negative evidence, whether it is more likely than not that some or all of the deferred tax assets will not be realized. In evaluating the need for a valuation allowance, Autodesk considered cumulative losses arising from the Company's business model transition as a significant piece of negative evidence. Consequently, Autodesk determined that a valuation allowance was required on the accumulated U.S., Canada and Singapore tax attributes. In the current year, the U.S. created incremental deferred tax assets, primarily operating losses, foreign tax and R&D credits, Singapore generated operating losses and Canada generated R&D credits. These U.S. and Singapore deferred tax attributes have been offset by a full valuation allowance. The valuation allowance increased by $163.6 million in fiscal 2019 primarily due to the generation of deferred tax attributes. The valuation allowance decreased by $113.8 million, and increased $352.4 million in fiscal 2018, and 2017, respectively, primarily related to U.S. Tax Act reduction in rate in fiscal 2018 and U.S. and Canadian deferred tax attributes generated in fiscal 2017. As Autodesk continually strives to optimize the overall business model, tax planning strategies may become feasible and prudent allowing the Company to realize many of the deferred tax assets that are offset by a valuation allowance; therefore, Autodesk will continue to evaluate the ability to utilize the net deferred tax assets each quarter, both in the U.S. and in foreign jurisdictions, based on all available evidence, both positive and negative.
The Tax Act was signed into law on December 22, 2017 and provided broad and significant changes to the U.S. corporate income tax regime. In light of our fiscal year-end, the Tax Act reduced the statutory federal corporate rate from 35% to 33.81% for fiscal 2018 and to 21% for fiscal 2019 and forward. The Tax Act also, among many other provisions, imposed a one-time mandatory tax on accumulated earnings of foreign subsidiaries (commonly referred to as the "transition tax"), subjected the deemed intangible income of our foreign subsidiaries to current U.S. taxation (commonly referred to as "GILTI"), provided for a full dividends received deduction upon repatriation of untaxed earnings of our foreign subsidiaries, imposed a minimum taxation (without most tax credits) on modified taxable income, which is generally taxable income without deductions for payments to related foreign companies (commonly referred to as “BEAT”), modified the accelerated depreciation deduction rules, and made updates to the deductibility of certain expenses. We have completed our determination of the accounting implications of the Tax Act on our tax accruals.
We recorded a tax benefit of the Tax Act in our financial statements as of January 31, 2018 of approximately $32.3 million mainly driven by the corporate rate remeasurement of the indefinite-lived intangible deferred tax liability.
As of January 31, 2018, we estimated taxable income associated with offshore earnings of $831.5 million, and as of January 31, 2019, we adjusted the taxable income to $819.6 million to reflect the impact of Treasury Regulations issued in the fourth quarter of fiscal 2019. Transition tax related to adjustments in the offshore earnings resulted in no impact to the effective tax rate as it is primarily offset by net operating losses that are subject to a full valuation allowance. As a result of the transition tax, we recorded a deferred tax asset of approximately $45.1 million for foreign tax credits, which are also subject to a full valuation allowance.
Table:
 | January 31, | 
 | 2019 | 2018
Stock-based compensation | $25.9 | $26.7
Research and development tax credit carryforwards | 238.7 | 170.3
Foreign tax credit carryforwards | 198.6 | 162.2
Accrued compensation and benefits | 6.5 | 25.9
Other accruals not currently deductible for tax | 19.0 | 22.9
Purchased technology and capitalized software | 32.6 | 43.4
Fixed assets | 15.0 | 16.5
Tax loss carryforwards | 237.2 | 85.7
Deferred revenue | 49.0 | 120.3
Other | 28.4 | 32.4
Total deferred tax assets | 850.9 | 706.3
Less: valuation allowance | (797.8) | (634.2)
Net deferred tax assets | 53.1 | 72.1
Indefinite lived intangibles | (67.6) | (57.0)
Total deferred tax liabilities | (67.6) | (57.0)
Net deferred tax assets (liabilities) | $(14.5) | $15.1


Question: What is Autodesk's tax expense primarily driven by?
Answer: Autodesk’s tax expense is primarily driven by tax expense in foreign locations, withholding taxes on payments made to the U.S. from foreign sources, and tax amortization on indefinite-lived intangibles offset by a tax benefit resulting from release of uncertain tax positions upon finalization of IRS examination and release of valuation allowance from acquired deferred tax liabilities.