Difficulty: Intermediate to Advanced | Prerequisites: Understanding of the income statement, the difference between GAAP and taxable income, and basic journal entries for income tax expense.
Income tax accounting bridges the gap between financial reporting (GAAP) and tax reporting (the Internal Revenue Code). Because the two systems recognise revenues and expenses on different schedules, pretax accounting income almost never equals taxable income. The differences create deferred tax assets and liabilities that appear on the balance sheet.
This topic is essential because deferred taxes affect reported earnings, cash flow, and balance sheet ratios. Analysts, auditors, and lenders all scrutinise deferred tax balances. The Tax Cuts and Jobs Act of 2017 introduced major changes to net operating loss treatment, and tax rate changes can force immediate adjustments to existing deferred tax balances.
You should already be comfortable with the basic income tax journal entry (debit Income Tax Expense, credit Income Tax Payable) before working through this material.
Temporary differences between GAAP and tax income reverse over time, creating deferred tax assets (future deductible amounts) or deferred tax liabilities (future taxable amounts). Permanent differences never reverse and create no deferred taxes. The valuation allowance reduces a DTA when it is more likely than not (>50%) that the benefit will not be realised. Under the TCJA, post-2017 NOLs can be carried forward indefinitely but are limited to 80% of taxable income, with no carryback. When enacted tax rates change, existing deferred tax balances must be remeasured immediately.
Temporary Difference
A difference between the tax basis and the book basis of an asset or liability that will reverse in a future period, giving rise to either a deferred tax asset or a deferred tax liability.
In simple terms, a timing mismatch: GAAP and the tax code agree on the total, just not when to recognise it.
Permanent Difference
A difference between pretax accounting income and taxable income that will never reverse. Examples include municipal bond interest (tax-exempt) and non-deductible fines. Permanent differences do not create deferred taxes.
Deferred Tax Liability (DTL)
Arises when a temporary difference results in a future taxable amount, meaning the company will owe more tax in the future than it would based on current GAAP income alone. Common cause: accelerated depreciation for tax purposes.
Deferred Tax Asset (DTA)
Arises when a temporary difference results in a future deductible amount, meaning the company will pay less tax in the future. Common cause: warranty expense recognised for GAAP before it is deductible for tax.
Valuation Allowance
A contra-asset account that reduces a DTA to its estimated realisable value. Required when it is "more likely than not" (probability greater than 50%) that some or all of the DTA will not be realised due to insufficient future taxable income.
Net Operating Loss (NOL)
Occurs when tax-deductible expenses exceed taxable revenues in a given year. The resulting loss can be carried forward to reduce taxable income in future years.
Statutory Tax Rate
The tax rate enacted into law for a given period. This is the rate used to measure deferred tax assets and liabilities.
Enacted Tax Rate
The rate that has been signed into law (not just proposed). Deferred taxes must always be measured at the enacted rate expected to apply when the temporary difference reverses.
Default Risk
The risk that a borrower will be unable to pay interest or principal on a debt. The Interest Coverage Ratio is a common measure lenders use to assess this risk.
Temporary differences reverse over time. They create deferred tax assets or liabilities.
Accelerated depreciation for tax, straight-line for GAAP: the tax deduction is larger early on (creating a DTL), but the total depreciation is the same over the asset's life. This is the most common temporary difference tested.
Warranty expense recognised at the time of sale for GAAP, but deductible only when paid for tax: creates a DTA because the company has a future deduction coming.
Instalment sales recognised on an accrual basis for GAAP but on a cash basis for tax: creates a DTL because taxable income will be higher in the future when cash is collected.
Permanent differences never reverse. They do not create deferred taxes.
Interest received on state and municipal bonds: included in GAAP pretax income but permanently excluded from taxable income. This is the classic example tested on exams.
Non-deductible fines and penalties: included in GAAP expense but never deductible for tax.
Life insurance premiums on key employees (when the company is the beneficiary): expensed for GAAP but not deductible for tax.
The key test: will the difference between book and tax treatment ever reverse? If yes, it is temporary. If no, it is permanent.
Deferred Tax Liability (DTL)
A future taxable amount creates a DTL. The most common example: a company uses MACRS (accelerated) depreciation for tax but straight-line for GAAP. In the early years, the tax deduction exceeds the book expense, so taxable income is lower than pretax accounting income. The difference reverses in later years, creating a future tax obligation.
DTL = Cumulative Temporary Difference x Enacted Tax Rate
Deferred Tax Asset (DTA)
A future deductible amount creates a DTA. Example: warranty expense of $100,000 is recognised for GAAP in Year 1 but is not deductible for tax until the warranty claims are paid in Year 3. The company has a future deduction coming, which will reduce future taxes.
DTA = Cumulative Temporary Difference x Enacted Tax Rate
Valuation Allowance
If, based on available evidence, it is more likely than not (>50% probability) that some or all of a DTA will not be realised, the company must establish a valuation allowance. This is a contra-asset that reduces the DTA on the balance sheet.
The journal entry to establish it: Debit Income Tax Expense, Credit Valuation Allowance.
The effect: current-year income tax expense increases, reducing net income.
The assessment considers all available evidence: future taxable income projections, existing taxable temporary differences that will reverse, tax-planning strategies, and recent earnings history.
The Tax Cuts and Jobs Act of 2017 changed how net operating losses are treated for NOLs arising after 31 December 2017.
No carryback: Post-2017 NOLs cannot be carried back to prior years to receive a tax refund. (Pre-2018 NOLs could be carried back two years.)
Indefinite carryforward: Post-2017 NOLs can be carried forward indefinitely. (Pre-2018 NOLs could be carried forward only 20 years.)
80% limitation: In any given year, the NOL deduction is limited to 80% of that year's taxable income (before the NOL deduction). The remaining 20% of taxable income is always subject to tax.
The combination of indefinite carryforward and the 80% cap means NOLs are never wasted, but they also never completely eliminate tax in a profitable year.
When a new tax rate is enacted, all existing deferred tax assets and liabilities must be remeasured immediately using the new rate. The adjustment flows through income tax expense (benefit) in the period of enactment.
Worked example (from the practice exam):
Alpha Corp. has a DTL of $12,000, computed at the old enacted rate of 30%.
Find the underlying temporary difference: $12,000 / 0.30 = $40,000.
Remeasure at the new enacted rate of 25%: $40,000 x 0.25 = $10,000.
The required adjustment: $12,000 - $10,000 = $2,000 decrease.
Journal entry:
Debit Deferred Tax Liability $2,000
Credit Income Tax Expense (Benefit) $2,000
The decrease in the DTL is a benefit: the company's future tax obligation has fallen, so current-period income tax expense is reduced.
Deferred Tax Liability = Cumulative Taxable Temporary Difference x Enacted Tax Rate
Deferred Tax Asset = Cumulative Deductible Temporary Difference x Enacted Tax Rate
Income Tax Expense = Current Tax Payable + Change in DTL - Change in DTA + Change in Valuation Allowance
Underlying Temporary Difference = Existing DTL (or DTA) / Old Enacted Tax Rate
New DTL (or DTA) after rate change = Underlying Temporary Difference x New Enacted Tax Rate
Adjustment = Old Balance - New Balance
Students often treat municipal bond interest as a temporary difference. It is permanent. The interest is never taxed, so the difference between book and tax income never reverses.
Students sometimes believe that establishing a valuation allowance eliminates the DTA. It does not. The DTA remains on the books; the valuation allowance is a contra-account that reduces its net carrying amount.
Students confuse the direction of the tax rate change adjustment. A decrease in the enacted rate reduces both DTLs and DTAs. For a DTL, this is a benefit (credit to income tax expense). For a DTA, this is a charge (debit to income tax expense).
Students assume NOLs can still be carried back under current law. For NOLs arising after 2017, the TCJA eliminated carrybacks entirely.
Students sometimes conflate the statutory rate with the effective rate. The statutory rate is what the law says; the effective rate is the actual income tax expense divided by pretax accounting income.
⚠️ Permanent vs. temporary: know the classic examples of each. Municipal bond interest (permanent) and accelerated depreciation (temporary) are the two most commonly tested.
⚠️ The valuation allowance threshold: "more likely than not" means greater than 50% probability. Know the journal entry (Debit Income Tax Expense, Credit Valuation Allowance).
⚠️ NOL rules under TCJA: indefinite carryforward, 80% limitation, no carryback. These appear in multiple question formats.
⚠️ Tax rate change adjustments: be prepared to calculate the new DTL/DTA balance and write the journal entry. The worked example above is representative of what the exam tests.
⚠️ Fill-in-the-blank favourites: "statutory" tax rate, "valuation allowance," "permanent" difference, "deferred tax liability" from a future taxable amount.
Fill in the blank: Interest on municipal bonds creates a ______ difference. (Permanent.)
True or false: Under the TCJA, post-2017 NOLs can be carried back two years. (False.)
Fill in the blank: The ______ is used to reduce a DTA if its realisation is not probable. (Valuation allowance.)
Fill in the blank: The TCJA limits NOL carryforwards to ______ of taxable income. (80%.)
True or false: A future taxable amount results in a deferred tax asset. (False, a deferred tax liability.)
Q: Which of the following results in a permanent difference: (a) MACRS vs. straight-line depreciation, (b) warranty expense timing, (c) interest on municipal bonds, (d) instalment sales?
A: (c) Interest on municipal bonds. It is included in GAAP income but permanently excluded from taxable income.
Q: Define the valuation allowance for DTAs and state the probability threshold.
A: A contra-asset account that reduces the DTA to its estimated realisable value. It is required when it is "more likely than not" (greater than 50% probability) that some or all of the DTA will not be realised.
Q: Alpha Corp. has a DTL of $12,000 at 30%. The rate changes to 25%. Calculate the adjustment and provide the journal entry.
A: Temporary difference = $12,000 / 0.30 = $40,000. New DTL = $40,000 x 0.25 = $10,000. Adjustment = $2,000 decrease. Debit DTL $2,000, Credit Income Tax Expense $2,000.
Q: Under the TCJA, how are post-2017 NOLs treated?
A: They can be carried forward indefinitely, but the deduction in any year is limited to 80% of that year's taxable income. No carryback is permitted.
Deferred taxes interact with investments: unrealised gains on AFS securities create temporary differences, and the CECL allowance for HTM securities has its own deferred tax effects.
Lease accounting creates temporary differences when GAAP lease expense differs from the tax deduction for the lease payment.
Share-based compensation generates deferred tax assets because the compensation expense recognised for GAAP is typically deductible for tax only when the options are exercised or the shares vest.
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