Bookkeeping · Reconciliation & Close · Guide · Intro level
Bank reconciliation from first principles
How to reconcile a bank account: why the book balance and bank balance differ, the step-by-step procedure, a fully worked example, and how to diagnose a reconciliation that will not balance.
Reconciling a bank account means proving that the cash balance in your books and the balance the bank reports are two views of the same reality — and explaining, dollar for dollar, why they differ on any given day. The two numbers almost never match on their own, and that is normal: your books know about checks the bank has not seen, and the bank knows about fees your books have not seen. The reconciliation is the bridge between them, rebuilt every month.
This is the single most important control in small-business bookkeeping. It catches your errors, the bank's errors, duplicate entries, missed fees, and — not rarely — fraud. Skip it for six months and your cash balance becomes an opinion.
Why the two balances differ
On any given date the bank and your ledger each know things the other does not. Every legitimate difference falls into one of four families.
The four reasons book and bank disagree, and which side is behind:
| Difference | Who knows about it first | Example | Fix |
|---|---|---|---|
| Deposits in transit | Your books | Friday's deposit recorded in the ledger; bank posts it Monday | None — it clears itself |
| Outstanding checks | Your books | Check #1042 mailed on the 28th, cashed on the 5th | None — it clears itself |
| Unrecorded bank items | The bank | Monthly service fee, interest earned, NSF returned check, autopay debit | Record them in your books |
| Errors | Either side | You entered 541 as 514; bank posted a deposit twice | Correct your books, or dispute with the bank |
Notice the asymmetry. Timing differences need no entry — they resolve on their own as items clear. Bank items and your own errors require journal entries. Bank errors require a phone call, and they are rarer than beginners hope.
The reconciliation procedure, step by step
Work from the bank statement, not from memory, and reconcile to the statement's closing date.
- Gather the bank statement and your ledger's cash account activity for the same period.
- Confirm the starting point: last month's reconciled balance must equal this statement's opening balance. If it does not, stop — a prior reconciliation was changed or never finished. See reopening discipline in the close checklist.
- Tick off every deposit on the statement against deposits in your books. Anything in your books but not on the statement is a deposit in transit. Anything on the statement but not in your books needs to be recorded (or investigated).
- Tick off every withdrawal, check, and debit the same way. Book-only items are outstanding checks or payments; statement-only items are unrecorded fees, interest, autopays, or errors.
- Record the bank-only items in your ledger — fees, interest, NSF items, direct debits.
- Compute the adjusted balances (worked below). They must be equal.
- Save the reconciliation report — the list of outstanding items is next month's starting point and the evidence the work was done.
A fully worked reconciliation
Suppose it is early June and you are reconciling May. The May 31 bank statement shows a closing balance of 14,280.00. Your ledger's cash account shows 13,655.00 on the same date. The difference to explain is 625.00.
Working the tick-off, you find:
- A deposit of 1,850.00 recorded May 30, posted by the bank June 2 (deposit in transit).
- Checks #2107 for 1,200.00 and #2109 for 310.00 not yet cleared (outstanding checks).
- A bank service fee of 25.00 on the statement, not in your books.
- Interest earned of 10.00 on the statement, not in your books.
- A vendor autopay of 1,270.00 debited May 28, never entered in the ledger.
The two-column proof — each side adjusted for what the other side knows:
| Bank side | Amount | Book side | Amount |
|---|---|---|---|
| Balance per bank statement | 14,280.00 | Balance per books | 13,655.00 |
| Add: deposit in transit | 1,850.00 | Add: interest earned | 10.00 |
| Less: check #2107 | (1,200.00) | Less: bank service fee | (25.00) |
| Less: check #2109 | (310.00) | Less: unrecorded autopay | (1,270.00) |
| Adjusted bank balance | 14,620.00 | Adjusted book balance | 12,370.00 |
The sides do not agree — 14,620.00 versus 12,370.00, a difference of 2,250.00. Good: this is what a real reconciliation feels like mid-stream. Divide the difference by 2 and you get 1,125.00; nothing matches that. Check divisibility by 9: 2,250 ÷ 9 = 250, so a transposition is possible. Re-checking the deposit slips, you find the May 30 deposit was actually 4,100.00, entered in the books correctly but listed in your reconciliation as 1,850.00 — a worksheet error of 2,250.00. Correcting the deposit-in-transit line to 4,100.00 makes the adjusted bank balance 16,870.00... which now overshoots. That tells you the books also carried the deposit at 1,850.00 and are short the same 2,250.00 — the deposit was under-recorded in the ledger too. Book the correction, and both adjusted balances settle at 14,620.00. The reconciliation balances, and it caught a real revenue understatement.
The book-side items require entries. The fees and interest:
| Account | Debit | Credit |
|---|---|---|
| Bank service charges | 25.00 | |
| Cash | 25.00 | |
| Cash | 10.00 | |
| Interest income | 10.00 |
Two entries shown in one figure. The unrecorded autopay gets a third entry, debiting the relevant expense account for 1,270.00 and crediting Cash.
The bank-side items — the deposit in transit and outstanding checks — get no entry. They are already in your books; the bank simply has not caught up.
What "reconciled" means
Both adjusted balances agree, every statement line is matched or recorded, every book entry is matched or listed as outstanding, and the report is saved. The adjusted balance — 14,620.00 in the example — is your true cash position, the number that belongs on the balance sheet. Neither the raw bank balance nor the unadjusted book balance is the truth; the reconciliation is.
When it will not balance: the difference-diagnosis table
When the adjusted balances refuse to agree, do not re-tick everything randomly. Compute the exact difference and interrogate it — the number itself often names the error.
Diagnosing a stubborn difference by its arithmetic signature:
| The difference is… | Likely cause | What to do |
|---|---|---|
| Exactly equal to one transaction | That item ticked twice, or missed entirely | Search both sides for the exact amount |
| Evenly divisible by 9 | Transposition (541 → 514) or slide (541.00 → 54.10) | Scan entries for swapped digits; slides are also ÷ 9 |
| Exactly twice a transaction | Item posted to the wrong side (debit as credit) | Halve the difference and search for that amount |
| A round number (100.00, 500.00) | Data-entry keystroke error | Compare source documents to entries |
| Equal to last month's difference | Prior reconciliation forced or unfinished | Re-open last month; fix the starting point |
| Small and shrinking as you work | Multiple small unrecorded fees | Comb the statement for fee lines |
Two tricks earn their keep. Divide by 9: the difference between any number and a transposition of its digits is always a multiple of 9, so a difference like 63, 270, or 2,250 points to swapped digits. Divide by 2: an entry posted to the wrong side of the account throws the reconciliation off by double the amount, so halve the difference and hunt for that figure. A longer diagnostic sequence — ordered by how often each cause occurs — is in reconciliation discrepancy hunting.
What the reconciliation protects you from
The reconciliation is a control, not a chore, and it is worth naming what it actually catches:
- Your errors — duplicates, transpositions, missed entries — before they hit financial statements or a tax return.
- Bank errors — rare, but real, and disputes have time limits.
- Fraud — forged checks, unauthorized ACH debits, and skimmed deposits surface as unmatched items. Regulation E and UCC Article 4 dispute windows are short; a business that reconciles monthly finds unauthorized debits inside the window, and one that reconciles annually usually does not.
- Fee creep — recurring charges nobody approved.
The IRS's recordkeeping guidance in Publication 583 treats reconciled bank records as a backbone of an adequate books-and-records system, and under Section 6001 taxpayers must keep records sufficient to establish income and deductions — a cash account that ties to bank statements is the cleanest evidence there is. Publication 538 adds the accounting-period discipline: income and expenses belong in the right period, which is precisely what timing differences, left unmanaged, corrupt.
Where this fits in the monthly close
Bank reconciliation is step one of the month-end close — nothing downstream (accrual review, statements, locking the period) is trustworthy until cash is proven. The full sequence lives in the month-end close checklist, and the same tick-and-prove discipline extends to credit cards, payment processors, and loan balances — a schedule of what to reconcile and how often is in the reconciliation frequency guide.
When does formal monthly reconciliation not make sense? Almost never for an operating account. The honest exceptions are dormant accounts with no activity (an annual confirmation suffices) and the first messy months of a new business before a ledger exists — in which case the fix is to start the ledger from a clean, dated opening balance, as described in opening balance problems, not to skip the control.
Frequently asked questions
- What is a bank reconciliation?
- A bank reconciliation is the monthly process of comparing the cash balance in your books to the balance on the bank statement and explaining every difference. Legitimate differences come from timing — deposits in transit and outstanding checks — plus bank fees and interest you have not yet recorded. Anything left over is an error, in your books or the bank's.
- Why doesn't my book balance match the bank statement?
- Four causes explain nearly every difference: deposits recorded in your books that the bank has not yet posted, checks you wrote that have not cleared, bank items (fees, interest, direct debits) not yet in your books, and outright errors. A reconciliation sorts each dollar of difference into one of those buckets until nothing is unexplained.
- How often should I reconcile my bank account?
- Monthly, within a few days of the statement date, for every operating account. Monthly reconciliation keeps the search window small — a missing $50 is easy to find among 40 transactions and miserable among 500. High-volume accounts benefit from a weekly review of cleared transactions, with the formal reconciliation still done monthly.
- What does it mean if my reconciliation difference is divisible by 9?
- A difference evenly divisible by 9 usually signals a transposition error — two digits swapped when a number was entered, such as 541 typed as 514. The difference between any number and its transposition is always a multiple of 9. Scan recent entries for amounts whose digits could have been reversed.
- Should I reconcile to the statement date or to month-end?
- Reconcile to the bank statement's closing date, because that is the only date the bank certifies a balance for. If your statement cycle does not end on the last day of the month, ask the bank to switch to calendar-month statements; most will. Otherwise reconcile to the cycle date and roll forward.