How to Calculate Income Tax Expense: Step-by-Step Guide

Quick Answer: Income tax expense equals current tax (tax payable now) plus deferred tax (future tax effects of temporary differences). Start with accounting profit, apply permanent adjustments, calculate taxable profit, then determine current and deferred tax components.

Key Takeaways

Income tax expense = Current tax + Deferred tax — not just taxes you owe this year.
Start with accounting profit, then reconcile to taxable profit using permanent and temporary differences.
Current tax is based on taxable profit × enacted tax rate.
Deferred tax captures timing differences that will reverse in future periods.
The effective tax rate (ETR) reconciliation explains why your ETR differs from the statutory rate.
Always document your calculation — tax authorities and auditors will ask.

What Is Income Tax Expense?

Income tax expense is the total tax charge recognized in the income statement for a period. It comprises two distinct components:

Current tax: The amount of income taxes payable for the current period based on taxable profit.
Deferred tax: The future tax consequences of temporary differences between accounting and tax treatment.

This follows the balance sheet approach under IAS 12 (IFRS) and ASC 740 (US GAAP). Rather than simply reporting taxes paid, you recognize the total economic tax burden including timing differences.

Income Tax Expense = Current Tax ± Deferred Tax

The Calculation Process: Step-by-Step

Step 1: Start with Accounting Profit Before Tax

Use the accounting profit before income tax from your income statement. This is your starting point.

Step 2: Adjust for Permanent Differences

Adjust accounting profit for items that never reverse:

Non-taxable income — subtract from accounting profit (e.g., municipal bond interest)
Non-deductible expenses — add to accounting profit (e.g., fines, penalties, entertainment over limits)

Step 3: Adjust for Temporary Differences

Adjust for timing differences that will reverse:

Taxable temporary differences — add to accounting profit (you'll pay tax later)
Deductible temporary differences — subtract from accounting profit (you'll save tax later)

Step 4: Calculate Taxable Profit

Taxable Profit = Accounting Profit
+ Non-deductible expenses
- Non-taxable income
+ Taxable temporary differences
- Deductible temporary differences

Step 5: Calculate Current Tax

Current Tax = Taxable Profit × Enacted Tax Rate

Step 6: Calculate Deferred Tax

Apply the expected future tax rate to net temporary differences:

Deferred Tax Liability = Taxable Temp Differences × Future Rate
Deferred Tax Asset = Deductible Temp Differences × Future Rate

Step 7: Calculate Total Income Tax Expense

Income Tax Expense = Current Tax + DTL - DTA

Complete Example

A Canadian corporation reports for Year 2026 (25% tax rate):

Accounting profit before tax	$1,000,000
Non-deductible meals & entertainment	$20,000
Tax-exempt municipal bond interest	($15,000)
Excess tax depreciation (tax > books)	$50,000
Warranty provision expensed, not deducted	$30,000

Calculation Walkthrough

Taxable profit calculation:

Accounting profit before tax	$1,000,000
+ Non-deductible meals & entertainment	+ $20,000
- Tax-exempt interest	- $15,000
+ Excess tax depreciation (taxable temp diff)	+ $50,000
- Warranty provision (deductible temp diff)	- $30,000
= Taxable profit	$1,025,000

Current tax: $1,025,000 × 25% = $256,250

Deferred tax:

Taxable temp difference (depreciation): $50,000 × 25% = $12,500 DTL
Deductible temp difference (warranty): $30,000 × 25% = $7,500 DTA
Net deferred tax: $12,500 - $7,500 = $5,000 (increases expense)

Total Income Tax Expense: $256,250 (current) + $5,000 (deferred) = $261,250

Effective Tax Rate: $261,250 ÷ $1,000,000 = 26.1% (vs statutory 25%)

How to Calculate Income Tax Expense: Step-by-Step Guide