Mixing personal and business
Paying for groceries from the business account or a business bill from a personal card muddies profit and creates tax questions. The fix going forward is separate accounts. For past entries, move personal items to owner draws and business items paid personally to owner reimbursement or contributions, with a note.
Skipping reconciliations
Without a monthly reconciliation, duplicates, missing deposits and bank errors pile up. When you finally reconcile, a year of differences is hard to untangle. Do it monthly, and when behind, reconcile the oldest months first and work forward.
Never fix a difference with a plug entry to force a match. Find the cause.
Miscategorizing
Common examples are loan principal in expenses, equipment in repairs, owner deposits in income and sales tax as revenue. Run an expense report by vendor and a list of unusual accounts to find them. Correct each at the transaction level where possible.
Where a transaction has a bank match, edit the category rather than creating a journal entry.
Duplicates and missing records
Duplicates arise when a bill is entered and a bank feed also creates an expense. The fix is to match feed items to existing bills. Missing records come from cash sales, unrecorded transfers and untracked refunds. Use the deposit detail and statement as a check on revenue.
Check sales against deposits each month, allowing for fees and timing.
Ignoring tax liabilities
Payroll taxes and sales tax collected belong to the government, not the business. If they sit in the bank without being paid, the cash looks like yours. Set up liability accounts and compare the balance with filings. Pay on time, since penalties compound.
If you discover unfiled returns, speak to a CPA or enrolled agent about the right approach.
Weak documentation and delayed work
Missing receipts, vague memos and months of backlog are the root of many other mistakes. Set a weekly fifteen-minute routine for receipts and categorizing. Backlogs get harder every month.
When you find an error in a closed year, do not edit silently. Record a correcting entry, note it, and ask your tax preparer whether an amended return is needed.
If you inherit a mess, tackle it in a sensible order. First, reconcile bank and card accounts so cash is right. Second, clear uncategorized balances. Third, check receivables and payables against actual open items. Fourth, review loans, payroll and sales tax liabilities. Fifth, review equity and fixed assets. Working top down from cash means each later step builds on solid ground and your fixes do not get undone by earlier errors.
Finally, write down each fix you make, with the date and reason, in a running log. It helps your accountant, and it shows you which mistakes recur so you can change the habit behind them.
Common questions
How do I know my books are wrong?
Red flags include a balance sheet that does not match the bank, large uncategorized balances and profit that does not fit your cash experience.
Should I fix old errors myself?
Small ones, yes. Larger or tax-related ones should be reviewed by a bookkeeper or CPA.
Can software prevent these mistakes?
It reduces them, but review and reconciliation are still needed.
This guide is general information, not tax, legal or accounting advice. Rules, fees and due dates change; check with the IRS, the NJ Division of Taxation or a licensed professional for your situation.