About Publication 535, Business Expenses Information about Publication 535, including recent updates, related forms, and instructions on how to file. This publication discusses common business expenses and explains what is and is not deductible. The chapters cover general rules for deducting business expenses and specific expenses. About Publication 538, Accounting Periods and Methods Publication 538 explains some of the rules for accounting periods and accounting methods. It is not intended as a guide to general business and tax accounting rules. About Publication 542, Corporations Publication 542 discusses the general tax laws that apply to ordinary domestic corporations. About Publication 947, Practice Before the IRS and Power of Attorney Publication 947 discusses who can represent a taxpayer before IRS and what forms or documents are used to authorize a representative. Usually, attorneys, CPAs, enrolled agents, and enrolled actuaries can represent taxpayers before IRS. This publication discusses who can represent a taxpayer before the IRS and what forms or documents are used to authorize a representative.