When the balance check isn't 0, don't type a plug to close the gap. Find the link that broke. The size of the gap is the best clue:
- The gap equals one line item: that line is missing somewhere, such as dividends left out of retained earnings, or D&A left out of PP&E.
- The gap equals twice a line item: that line has the wrong sign, such as an increase in inventory added to cash instead of subtracted.
- The gap grows every year: the error sits in a roll-forward (cash, PP&E, debt or retained earnings), so each year's mistake carries into the next year's opening balance.
Start with the first year that fails, because later years inherit its error. Check that the cash line picks up the whole net change in cash, then that every other balance sheet line rolls forward from its own schedule. Fix the formula, never the number, and confirm the check reads 0 in every year.