FAS 109, the accounting standard for income taxes, was reorganized into ASC 740 when the FASB codified U.S. GAAP, and the substance carried over unchanged. It governs how companies report income taxes in their financial statements, and it has two jobs: recognize the tax payable or refundable for the current year, and record deferred tax assets and liabilities for the future tax consequences of transactions already reflected in the books or the tax return. The framework uses an asset-and-liability approach anchored to the balance sheet. It measures the gap between what an asset or liability is worth for book purposes and what it is worth for tax purposes, and that gap drives the deferred tax calculation that ultimately shapes the tax expense line on the income statement.
Why Book and Tax Numbers Diverge
Deferred tax accounting exists because financial reporting rules and the tax code often recognize the same income or expense in different periods, and sometimes one system recognizes an item the other never will. Those mismatches fall into two categories, and the distinction determines whether the difference produces a deferred tax balance at all.
Temporary Differences
A temporary difference exists when book and tax will eventually recognize the same total amount, just on different schedules. Because the difference is guaranteed to reverse, it creates either a deferred tax asset (DTA) or a deferred tax liability (DTL).
Depreciation is the textbook case. A company might use accelerated depreciation on its tax return and straight-line depreciation for its financial statements. In the early years, tax depreciation runs ahead of book depreciation, so the company pays less tax now and will pay more later when the pattern reverses. That future payment is a DTL. Flip the pattern and you get a DTA: when a company books an allowance for doubtful accounts as an expense but cannot deduct it for tax purposes until the debt is actually worthless, the future tax benefit sits on the balance sheet as an asset.
Stock-based compensation works the same way. A company records compensation expense for nonqualified stock options over the vesting period, but the tax deduction does not arrive until exercise. That mismatch produces a DTA. When exercise finally happens, the deduction may be larger or smaller than the cumulative book expense, and any difference between the two hits income tax expense in the period of exercise.
Permanent Differences
Permanent differences are items that one system recognizes and the other never will. They shift the effective tax rate but produce no deferred tax balance, because nothing is scheduled to reverse.
Interest income from tax-exempt municipal bonds is included in book income but never taxed. Fines and penalties paid to a government reduce book income but are not deductible. Entertainment expenses are permanently nondeductible, and only 50% of meals expenses can be deducted. Incentive stock options generate a book compensation expense with no corresponding corporate tax deduction, so they too create a permanent difference. Items like these are why a company’s effective tax rate almost never lines up exactly with the statutory rate.
Calculating Deferred Tax Assets and Liabilities
The mechanics start with a comparison. For every asset and liability on the balance sheet, the book carrying amount is compared to the tax basis. The difference is the cumulative temporary difference. Multiplying that difference by the enacted tax rate expected to apply when it reverses produces the DTA or DTL.
Two measurement rules govern the calculation. Only enacted tax rates can be used. Proposed or anticipated changes, even ones that look inevitable, do not count until they become law. And deferred tax balances are never discounted to present value. A DTL that reverses in 20 years carries the same balance as one reversing next year, all else equal.
A DTL is a future tax payment: the company got a current tax benefit and owes it back later. A DTA is a future tax saving: the company paid more tax now and will recover the benefit later. The deferred tax expense or benefit shown on the income statement is simply the net change in all DTA and DTL balances from one period to the next.
Multi-state operations complicate the picture. Each state has its own rate, apportionment formula, and conformity rules. A temporary difference may reverse at a blended state rate that differs from the rate in effect when it originated, especially if the company’s geographic footprint shifts over time. State deferred taxes are calculated separately and layered on top of the federal computation.
Valuation Allowance
Carrying a DTA assumes the company will generate enough future taxable income to use the benefit. ASC 740 requires that assumption to be tested. A DTA stays on the balance sheet only if it is more likely than not, meaning greater than 50% probability, that the benefit will actually be realized.
When that threshold is not met, the company records a valuation allowance, a contra-asset that reduces the gross DTA to what it expects to recover. Recording a valuation allowance increases income tax expense in the period, and the swing can be large enough to move reported earnings meaningfully.
The assessment weighs all available evidence, positive and negative, with more weight given to objective, verifiable evidence than to subjective projections. ASC 740 identifies four sources of taxable income that can support realization:
- Reversals of existing DTLs, where taxable temporary differences scheduled to reverse in the same period as deductible ones absorb the deductible amounts.
- Future taxable income from projected operating results, which carries less weight because it depends on management forecasts.
- Carryback to a prior year that generated taxable income, where the tax law permits it and a refund is essentially guaranteed.
- Tax-planning strategies management would undertake, even if not currently planned, to keep the DTA from expiring unused.
A cumulative pre-tax loss over recent years is one of the strongest pieces of negative evidence in the analysis. When a company has been losing money consistently, it becomes very difficult to argue that future profits will absorb the DTA. Overcoming that history requires concrete, objectively verifiable positive evidence, not optimism.
Net Operating Losses
A net operating loss arises when a company’s allowable deductions exceed its gross income for the year. The NOL creates a deductible temporary difference and is recognized immediately as a DTA, representing the future tax savings the company expects when it uses the loss.
Federal Carryforward Rules
NOLs arising in taxable years beginning after December 31, 2017 can be carried forward indefinitely and never expire. The trade-off is a cap: the NOL deduction in any year is limited to 80% of taxable income computed before the NOL deduction itself. Under that cap, a profitable company with large NOL carryforwards will always owe some federal tax, because 20% of taxable income stays unshielded.
NOLs generated before 2018 followed different rules. They could be carried back two years and forward 20 years, with no percentage limitation on the deduction. Companies still holding pre-2018 NOLs have to track them separately because the usage mechanics differ.
Section 382 After an Ownership Change
When a company undergoes a significant ownership change, IRC Section 382 caps how much of its pre-change NOLs can be used each year. An ownership change occurs when one or more shareholders owning at least 5% of the stock increase their combined ownership by more than 50 percentage points over a three-year testing period. The annual limitation equals the value of the company’s equity immediately before the change, multiplied by the IRS-published long-term tax-exempt rate.
The rule catches more companies than most expect. Mergers and acquisitions are not the only triggers. Issuing new shares in a public offering, converting debt to equity, or granting large equity awards can shift ownership enough to cross the threshold. When an ownership change occurs, the DTA must be reduced to reflect the annual cap on NOL usage, and any excess that cannot be used within the limitation period may require a valuation allowance.
Multiple ownership changes compound the problem. Each new change imposes a separate limitation on all pre-existing tax attributes, including NOLs already subject to an earlier Section 382 cap. Companies with frequent equity transactions have to monitor ownership shifts continuously rather than testing only at the time of major deals.
Accounting for Tax Rate Changes
When a new tax rate is enacted, every existing DTA and DTL on the balance sheet must be remeasured immediately using the new rate. The adjustment flows through income tax expense from continuing operations in the period of enactment. It is not spread over future periods and not apportioned among interim quarters.
That can produce dramatic earnings swings. When the federal corporate rate dropped from 35% to 21% under the Tax Cuts and Jobs Act in 2017, companies with large DTLs recorded one-time tax benefits because their future obligations shrank, while companies with large DTAs took charges because their future savings were now worth less. The 21% federal corporate rate remains in effect for 2026.
The same treatment applies to state rate changes. If a state enacts a rate reduction effective in a future year, the company must remeasure deferred tax balances attributable to that state right away, using the rate that will be in effect when each temporary difference reverses.
Uncertain Tax Positions
Companies sometimes take positions on their tax returns that could be challenged by the IRS or another taxing authority. ASC 740 uses a two-step process to decide how much of the benefit can be reflected in the financial statements.
Recognition
The first step asks whether the position is more likely than not to be sustained on its technical merits if examined by a taxing authority with full knowledge of the facts. That means a greater than 50% probability. If the position fails this test, no benefit is recognized in the financial statements at all, even if the full amount was claimed on the return.
Measurement
A position that passes recognition is then measured as the largest dollar amount with a cumulative probability greater than 50% of being realized upon settlement. It is not all-or-nothing. The company considers the range of possible outcomes and picks the largest amount where the odds still favor realization.
The gap between the benefit claimed on the return and the amount recognized in the financial statements becomes a liability for unrecognized tax benefits (UTBs). The company also accrues interest on the underpayment at the applicable statutory rate and records any required penalties. Companies elect, as an accounting policy, whether to classify interest and penalties within income tax expense or as a separate line item.
How the Numbers Land on the Financial Statements
Once the current and deferred tax amounts are calculated, several presentation rules control where they show up.
Intraperiod Allocation
Total income tax expense for a period does not all sit on one line. ASC 740 requires the total tax effect to be allocated across the components that gave rise to it. Continuing operations gets its allocation first. The remainder is spread across discontinued operations, other comprehensive income, and items charged directly to equity, using a with-and-without approach that isolates the tax effect of each item. The allocation matters because it keeps a tax effect generated by, say, a discontinued operation from artificially reducing the tax expense on continuing operations.
Interim Reporting
Quarterly filers face a practical problem: they need to report income tax expense each quarter without knowing how the full year will play out. ASC 740-270 solves it with an estimated annual effective tax rate (AETR). At the end of each interim period, the company estimates the full-year effective rate, applies it to year-to-date ordinary income, and books the current quarter’s tax expense as the difference between that year-to-date figure and what was recorded in prior quarters.
The AETR captures permanent differences, tax credits, foreign rate differentials, and the anticipated effect of temporary differences. Certain items are excluded from the AETR and treated as discrete events in the quarter they occur. The most common discrete item is the tax effect of stock-based compensation awards when the tax deduction differs from cumulative book expense. Significant unusual or infrequently occurring items also get discrete treatment. Because the method is forecast-based, a change in projected annual income can force a sharp catch-up adjustment in a single quarter, producing a tax expense figure that looks disconnected from that quarter’s actual results.
Balance Sheet Presentation
On a classified balance sheet, all DTAs and DTLs are presented as noncurrent, regardless of when the underlying temporary differences are expected to reverse. Companies must net DTAs and DTLs that belong to the same tax-paying entity within the same tax jurisdiction, so only a single net noncurrent asset or single net noncurrent liability appears for each jurisdiction. Netting across jurisdictions is not allowed. A company with operations in the U.S. and Germany shows a net U.S. deferred tax position and a separate net German position.
The liability for unrecognized tax benefits generally sits in noncurrent liabilities unless the company expects to settle within one year. When a UTB effectively reduces an NOL carryforward rather than requiring a cash payment, it is presented as a reduction of the related DTA instead of a separate liability.
Disclosures
ASC 740 requires extensive tax disclosures, and the requirements expanded significantly with ASU 2023-09, which took effect for public business entities in annual periods beginning after December 15, 2024. Non-public entities have an additional year to adopt.
Public business entities must disclose a reconciliation between the expected tax amount, computed by multiplying pre-tax income from continuing operations by the 21% federal statutory rate, and the actual income tax expense reported. Under ASU 2023-09, reconciling items must be broken into specific standardized categories rather than lumped into broad buckets. The reconciliation is presented in both percentages and dollar amounts, and any single reconciling item exceeding 5% of the expected tax must be further disaggregated by nature and jurisdiction.
Both public and non-public entities must now disclose income taxes paid, net of refunds, disaggregated by federal, state, and foreign jurisdictions. Any single jurisdiction where taxes paid exceed 5% of the total must be separately identified.
The broader disclosure package also includes the gross amounts of DTAs and DTLs before and after valuation allowance, the total valuation allowance balance and the net change during the year, a tabular roll-forward of UTBs showing increases and decreases from current-year and prior-year positions along with settlements and statute-of-limitations expirations, and the tax years that remain open to examination by major taxing jurisdictions. ASU 2023-09 also eliminated the prior requirement for public entities to disclose specific tax positions for which the total UTB is reasonably possible to change significantly within the next 12 months.1FASB. ASU 2023-09 Income Taxes (Topic 740) The intent was to replace forward-looking disclosures that were hard to audit with the enhanced tabular data described above.