No prescribed form
The IRS does not require a particular form of recordkeeping — it requires records sufficient to establish the income, deductions, and credits you claim. A single-member sole proprietor with a few hundred transactions a year can use a spreadsheet and a folder of receipts. A growing business with employees and inventory needs accounting software and a bookkeeper.
Separate business banking
Open a separate business checking account from day one. The cleanest single thing you can do for tax recordkeeping is to never run business and personal money through the same account. Audit defense, deduction substantiation, lender financial statements, partnership interests, and entity protection all benefit.
Receipt retention
Retain receipts for all deductible expenses. Modern best practice is to scan or photograph receipts immediately and discard the paper. The IRS accepts electronic copies. Keep them organized by year and category.
Mileage logs
Mileage requires contemporaneous logs (Section 274(d)). Use a smartphone tracker (MileIQ, Stride, Hurdlr, QuickBooks Self-Employed) that logs trips automatically. Tag business trips weekly. Reconstructed-from-memory logs years later are routinely disallowed in audit.
Retention period
Three years from the return due date for most records (the normal statute of limitations). Six years for substantial omissions of income (>25%). Seven years for losses on worthless securities or worthless debts. Indefinitely if you never file or file fraudulently. Property records (basis) until disposition plus three years.
Common mistakes worth avoiding
The recurring mistakes filers make on this topic cluster in three patterns: (1) optimizing for current-year tax at the expense of multi-year tax, (2) treating the choice as binary when the IRS framework actually allows nuance (partial elections, hybrid methods, year-by-year reassessments), and (3) deferring the analysis until the return is due rather than running it during the year when the result can still influence behavior. A short annual review — even thirty minutes — catches all three failure modes and replaces vague intuition with documented reasoning.
When to bring in a professional
DIY tax software handles most small-business returns competently, but a handful of situations reliably justify a CPA or enrolled agent: an entity formation or election, a multi-state filing situation, a significant fixed-asset purchase that triggers Section 179 or bonus depreciation modeling, a retirement-plan setup, an IRS notice or examination, and the year of an entity sale. Outside those situations, software plus an annual half-day of personal review produces a defensible return. The cheapest professional engagement is a one-hour consultation rather than a full-service tax-prep relationship.