Start by reconciling every bank and credit card account through December 31, every transaction matched, every balance confirmed against the actual statement. An unreconciled account is the single biggest source of delay once a return is being prepared, because the numbers on paper do not match what actually happened.
Next, clear the uncategorized transactions list down to zero. Anything sitting in "Uncategorized Expense" or "Ask My Accountant" at year-end either becomes a missed deduction or a back-and-forth email chain trying to remember what a charge from March actually was. Neither is a good outcome.
The Difference a Checklist Makes at Filing Time
Consider two nearly identical small businesses handing off their books to the same tax preparer in February. The first business runs a full year-end checklist in December: bank accounts reconciled, uncategorized transactions cleared, owner draws confirmed as equity rather than expense, 1099s prepared for contractors, and loan balances checked against year-end statements. Their tax preparer completes the return within a week, with no follow-up questions needed.
The second business hands over a QuickBooks file that hasn't been reconciled since August, with forty uncategorized transactions and an owner loan repayment recorded as business income. The tax preparer has to stop and go back to the client repeatedly with clarifying questions, delaying the return by several weeks and, because the preparer bills for the additional reconciliation work required before the return can even be started, adding a meaningfully larger invoice than the first business paid for the same size company. The checklist itself costs nothing but a few hours in December; skipping it costs real time and real money in February.
Confirm that any owner draws, capital contributions, and inter-account transfers are coded correctly, not as income or expense. This is the single most common cause of a balance sheet that will not balance once tax season starts, and it creates downstream errors in every financial statement built from those books.
Pull together 1099s for any contractor paid $600 or more during the year, these are due to recipients by January 31 and to the IRS shortly after. Reconcile loan balances against year-end statements, and confirm payroll totals match your filed 941s for all four quarters.
A business that runs this checklist every December hands off books that a tax preparer can move through quickly, instead of books that need to be rebuilt before the return can even start. The result is a faster return, fewer questions, and a higher likelihood that every legitimate deduction actually makes it onto the filing.
Reconciling Fixed Assets and Depreciation Schedules Too
Beyond bank accounts and 1099s, a genuinely complete year-end checklist includes reconciling your fixed asset register, confirming that equipment purchased during the year is properly recorded, prior years' depreciation schedules are updated, and anything sold or disposed of has been removed with any gain or loss properly recognized. This step gets skipped more than any other on this list, simply because fixed assets don't generate the same monthly transaction volume that bank reconciliation does, making it easy to forget entirely until the return is already being prepared.
An unreconciled fixed asset register is exactly the kind of gap that shows up as a mismatch between your books and your prior year's tax depreciation schedule, creating exactly the kind of back-and-forth with your preparer this checklist is meant to prevent.
Running this checklist in early December, rather than waiting until the last week of the year, also leaves enough time to actually fix anything it uncovers before the books officially close. Finding a reconciliation gap on December 30th leaves little room to investigate properly; finding the same gap in early December gives you weeks to trace it down correctly.