A correct sum can still be incomplete

A budget spreadsheet can calculate every visible row perfectly and still leave out important costs. Begin with the scope: which people, accounts and time period does it represent? A household total built only from one person's current account will miss purchases made elsewhere unless they are deliberately added.

Make a list of payment channels: bank accounts, cards, cash, digital wallets and any other method actually used. Compare that list with the spreadsheet's sources. Do not import sensitive login details or full account credentials into the workbook; an identifying label is enough for this check.

Reconcile one account before expanding

Choose a completed statement period. Starting balance plus incoming amounts minus outgoing amounts should agree with the ending balance, allowing for the statement's own conventions. If it does not, investigate missing rows, duplicate imports, reversed signs or dates outside the selected period. This account reconciliation is different from a spending-category total because transfers belong in the account calculation.

For a hypothetical account starting at 500, receiving 1,800 and paying out 1,950, the ending balance is 350. If the sheet shows 410, the unexplained difference is 60. Search for the discrepancy rather than entering a balancing adjustment immediately. A 60 payment may be missing, but several smaller errors could produce the same difference.

Look beyond the month

Review a year of records for costs absent from the current month: renewals, seasonal purchases, repairs and scheduled maintenance. Add a future allowance or a dated expense as appropriate. Do not add both the full future bill and its monthly reserve contribution as separate consumption costs in the same view.

Consider household changes too. A forthcoming move, new commute or change in care arrangements can make last year's record incomplete as a forecast even when it is accurate history. Keep these expected changes in a clearly labelled forecast area.

Inspect the spreadsheet mechanics

Check that totals include new rows at the bottom of each range. A formula ending on row 25 will not automatically include row 26 in every spreadsheet design. Look for numbers stored as text, hidden rows, active filters and formulas replaced accidentally by typed values.

Test one category manually using a few known transactions. If a lookup depends on exact category names, a trailing space or spelling variation may omit an entry. Use a visible unclassified total so unmatched transactions do not silently disappear.

Review signs on refunds and transfers. A refund recorded as another positive expense inflates spending; a transfer excluded from an account balance understates cash movement. The workbook should make clear which view each total represents.

Make the check repeatable

Keep a short control area showing the last statement date reconciled, the number of unclassified entries and any unresolved difference. Save a version before major structural changes so mistakes can be traced.

A passing formula check does not establish that a household can afford every planned cost. It establishes that the record is internally consistent. Compare the completed forecast with actual available income and payment dates separately. That final step turns a technically tidy sheet into a usable plan.

Check a duplicated import before deleting rows

A transaction export can overlap a previous download. Compare date, amount and description, but do not assume identical amounts are duplicates: two genuine purchases can occur at the same merchant on the same day. Use a transaction reference when the export provides one, or compare the source statement. Keep uncertain entries marked for review rather than deleting them to make a total look right.

If the spreadsheet uses both a transaction sheet and a summary, identify which is the source of truth. Correct an error in that source and allow the summary to update. Typing a compensating amount directly into the summary may hide the issue for one month while leaving future calculations inconsistent.