Key Takeaways

• The tax year (accounting period) and accounting method a business uses determine when income is reported and when expenses are deducted — these timing decisions can materially change the tax result even when the total amounts are the same.
• Most small businesses and sole proprietors use a calendar year and the cash method of accounting, but the publication explains when these defaults do not apply and when other methods must be used.
• Constructive receipt is a critical concept under the cash method: income is taxable when it is available to the taxpayer, even if the taxpayer has not yet collected it.
• Changing an accounting method requires IRS consent (usually by filing Form 3115), and unauthorized changes can create serious compliance problems.

Common Mistakes to Avoid

• Assuming every business can use the cash method — certain businesses with inventory or those exceeding specific gross receipts thresholds may be required to use the accrual method.
• Ignoring constructive receipt rules by delaying deposit of a check received in December to push income into the next tax year — the income is reportable in the year the check was available.
• Switching accounting methods without filing Form 3115, which can result in the IRS treating the method change as unauthorized and adjusting the return accordingly.
• Confusing bookkeeping records with tax accounting — a business may keep books on one basis and still need to make adjustments when preparing the tax return.

Section-by-Section Summary

Why timing is a core tax law issue rather than only a bookkeeping issue

Publication 538 begins by explaining that the timing of income and expense recognition is a substantive tax issue, not merely an administrative one. Two businesses with identical revenue and expenses can have different tax liabilities depending on their accounting method and tax year. The publication frames this as a foundational concept that affects virtually every line on a business return. For how business income flows to Schedule C, see our detailed guide.

How tax years and accounting periods are established

Most individuals and sole proprietors use a calendar year (January 1 through December 31). Corporations, partnerships, and other entities may use a fiscal year if they meet certain requirements. The publication explains how a tax year is adopted (generally by filing the first return using that period) and when a short tax year may occur (such as when a business starts or terminates mid-year). It also covers the rules for partnerships and S corporations, which generally must conform their tax year to the owners’ tax years unless an election is made.

How the cash method works and where constructive receipt matters

Under the cash method, income is reported when actually or constructively received, and expenses are deducted when paid. The cash method is simple and intuitive for most small businesses, but the constructive receipt doctrine adds an important nuance: income is taxable when it is credited to the taxpayer’s account, set aside, or otherwise made available without restriction, even if the taxpayer has not physically collected it. This means a check received on December 30 is taxable in that year even if not deposited until January. See our guide on cash basis income and expense reporting for more detail.

How the accrual method works and how it differs from cash accounting

Under the accrual method, income is reported when all events have occurred that fix the right to receive it and the amount can be determined with reasonable accuracy. Expenses are deducted when the liability is established and the amount can be determined, regardless of when payment is actually made. The accrual method is required for businesses that carry inventory (with some exceptions under the small business taxpayer rules) and for certain other entities. The publication explains the all-events test and the economic performance requirement that govern accrual-method deductions.

What special timing rules and method issues taxpayers should notice

The publication covers several special situations, including the uniform capitalization rules (which require certain costs to be capitalized into inventory or other property rather than deducted currently), the rules for long-term contracts, and the installment method for reporting gain from certain sales. It also explains how prepaid expenses are treated under both methods and when the 12-month rule allows immediate deduction of certain prepayments. These special rules are often where small businesses make errors because they conflict with the straightforward cash-basis intuition.

How changes in accounting method are handled

Changing an accounting method is not simply a bookkeeping decision — it requires IRS consent, typically obtained by filing Form 3115. The publication explains the difference between a change in accounting method (which requires consent) and a correction of an error (which does not). It also covers the section 481(a) adjustment, which is a cumulative catch-up adjustment that prevents items from being permanently omitted or double-counted when a method changes. Getting this adjustment right is essential to avoiding duplicate taxation or lost deductions. See also our guide on calculating business expenses.

Why Publication 538 is often a follow-on guide to Publication 334

Many small business owners first encounter accounting period and method questions while reading Publication 334 (the Tax Guide for Small Business). Publication 334 provides a general overview, but Publication 538 goes deeper on the timing rules that Publication 334 introduces. In practice, the two publications are often used together: Publication 334 identifies the issue, and Publication 538 provides the detailed guidance needed to resolve it correctly.

How readers should use it when a tax question is really a timing question

Many tax disputes that appear to be about amounts are actually about timing. If a taxpayer is wondering when to report a payment received, when to deduct an expense incurred, or whether a prepayment can be deducted immediately, Publication 538 is the right resource. The publication helps reframe these questions in terms of accounting period and method, which is how the IRS analyzes them. Starting with the timing framework often clarifies issues that seem confusing when approached from a forms-first perspective.

How to Use This Publication

Start by confirming which tax year and accounting method your business uses. If you are unsure, check the first return filed for the business. When timing questions arise during the year — such as when to recognize a large payment or how to handle a prepaid expense — consult the relevant sections. If you are considering a method change, review the Form 3115 requirements before making any changes on the return.

In practice, this publication is most often consulted when a business encounters a timing issue for the first time or when a preparer is evaluating whether a method change would benefit the client. It provides the conceptual framework that makes other business publications easier to apply correctly.

For related context, see our guides on Schedule C, cash basis income and expense reporting, and calculating business expenses.

Frequently Asked Questions

What does this IRS guide cover?

Publication 538 explains how tax years and accounting methods work, the differences between cash and accrual accounting for tax purposes, the constructive receipt doctrine, and how to change accounting methods.

Is this summary enough to file correctly?

No. This page is a practical summary. Businesses considering a method change or dealing with complex timing issues should review the official publication and consult Form 3115 instructions.

Who should read this page first?

New business owners choosing an accounting method, businesses with inventory, anyone considering a method change, and preparers dealing with income or expense timing questions.