What it means
The starting point for a company is the profit shown in its accounts, but that figure is almost never the figure that gets taxed. The tax code allows some costs the accounts do not, disallows others the accounts do, and uses its own depreciation timetable, so the two numbers diverge.
Those differences fall into two families. Permanent differences, such as fines or a portion of meal costs, never reverse, while temporary differences, such as depreciation taken faster for tax than for accounts, simply shift tax between years and give rise to deferred tax balances.
Companies do not wait until the year end to pay. Estimated federal income tax is paid in quarterly instalments based on projected profit, with a true-up when the return is filed, and underpaying the estimates attracts interest charges.
Individuals face a progressive structure, where successive slices of income are taxed at rising rates. A common misunderstanding is that moving into a higher bracket raises the tax on all income, when in fact only the income above the bracket threshold is taxed at the higher rate.
The number that matters in company reporting is the effective tax rate, meaning tax expense divided by pre-tax accounting profit. It rarely equals the statutory rate, and the reconciliation between the two, which listed companies must disclose, is one of the more revealing notes in a set of accounts.
In practice
Real-world examples
Example 1
A manufacturer buys $800,000 of machinery and claims accelerated depreciation for tax purposes while writing it off evenly over eight years in the accounts. Its cash tax bill drops sharply in year one, and the accounts carry a deferred tax liability for the difference.
Example 2
A profitable consultancy pays quarterly estimated tax of $95,000 based on forecast full-year profit. A large fourth-quarter contract loss reduces actual profit, and the company recovers the overpayment when it files its return.
Example 3
A start-up records a $1,400,000 loss in its first year and owes no federal income tax. It carries the loss forward and uses it to reduce taxable income once it turns profitable two years later.
Think of it
Think of federal income tax like a mandatory membership fee for using a massive shared community centre. The more income you generate, the larger your membership tier, and those pooled fees keep the lights on, the roads paved, and the security running for everyone.
Formula
Calculation
Federal income tax = taxable income x applicable rate, where taxable income = accounting profit adjusted for tax-specific additions and deductions
Clearwater Fixtures reports pre-tax accounting profit of $2,000,000 for the year. Its accountants add back $150,000 of costs the tax code does not permit as a deduction, and subtract $250,000 of additional depreciation the tax code allows but the accounts do not.
Taxable income: $2,000,000 + $150,000 - $250,000 = $1,900,000
Federal income tax at 21%: 21% x $1,900,000 = $399,000
Effective tax rate on accounting profit: $399,000 / $2,000,000 = 19.95%
The company pays less than 21% of its book profit this year only because the extra depreciation has been pulled forward. In later years that deduction is no longer available, taxable income exceeds accounting profit, and the effective rate rises above 21% until the difference has fully reversed.Case study
Seen in the real world
This illustrative and fictional case follows Sandhill Instruments, a scientific equipment maker with $6,000,000 of pre-tax accounting profit. Its chief executive was baffled that the tax charge in the accounts was $1,410,000, an effective rate of 23.5%, when the statutory federal rate was 21%.
The reconciliation explained it. Non-deductible items, mainly a $340,000 regulatory penalty and disallowed entertainment costs, added tax of about $75,000, and a valuation allowance against losses in a loss-making subsidiary added roughly $180,000, while a research credit reduced the charge by about $105,000.
The useful lesson for Sandhill's board was that only some of that gap was manageable. The penalty was a one-off, the research credit was worth claiming more systematically, and the subsidiary losses would only ever become valuable if that business returned to profit, which reframed the tax discussion as an operating question rather than a tax planning one.
Watch out
Common mistakes
- Assuming the tax charge equals accounting profit multiplied by the statutory rate. Permanent and temporary differences mean the two almost never match exactly.
- Believing a higher tax bracket applies to all of an individual's income. Only the portion of income above the bracket threshold is taxed at the higher rate.
- Forgetting state and local income taxes when budgeting. Federal tax is one layer, and combined rates in some states are materially higher than the federal figure alone suggests.
Questions
People also ask
What is the difference between current and deferred tax?
Current tax is the amount payable on this year's taxable income, while deferred tax records the future consequences of timing differences between accounting and tax treatment.
Why do companies pay tax quarterly?
The tax authorities require estimated payments through the year based on expected profit, with a balancing payment or refund when the annual return is filed.
Does a loss-making company always pay nothing?
Usually no federal income tax is due on the loss itself, but the company may still owe other taxes, and the loss only becomes valuable when it can be set against future profits.