Every conversion proves itself: how balance-checking works

When software hands you data extracted from a document, the honest question is: how do you know it's right? For most extraction tools the answer is "it usually is" — confidence expressed as a percentage, measured on someone else's documents. We built NoRekey around a stronger answer: every statement carries its own proof, and every conversion has to pass it.

The statement is a self-verifying document

A bank statement declares an opening balance, a closing balance, and the transactions between them. That structure is a gift: it means the correctness of an extraction isn't a matter of opinion. Sum the extracted amounts, walk the opening balance forward, and you either land on the declared closing balance to the penny or you don't.

opening + sum(amounts) == closing   (within 0.01)

Every NoRekey conversion runs this check before you see it. A statement with a hundred transactions across seven pages passes only if all hundred are present, correctly signed, and correctly read — a single dropped row, flipped sign or transposed digit breaks the chain. It's the same arithmetic a careful bookkeeper does by hand at month-end; we just refuse to skip it.

Running balances tighten the net further

Most statements also print a running balance beside transactions. That per-row trail lets verification act locally, not just end-to-end: the chain must agree at every printed balance, which pins any discrepancy to the exact row where it appears. It also enables something better than detection — provable repair. If a running balance disagrees with the amount chain but the magnitudes match exactly, precisely one sign is flipped, and the statement itself shows which; overdrawn balances marked "OD" are the classic case. We only ever correct what the document demonstrates, never what a heuristic guesses.

What you see

Every conversion carries its verdict. Balanced means the arithmetic proved out — the badge you'll see on the overwhelming majority of conversions. Needs review means it didn't, and we say so: you get the rows and the flag, so ninety seconds of attention goes exactly where it's needed instead of being spent re-checking everything. (Statements that declare no totals — some card statements, some app exports — can't be checked this way, and we mark that honestly rather than invent confidence.) There's a longer help-centre write-up here: how balance checking works.

Why this is the feature that matters

Extraction accuracy claims are unfalsifiable from the outside; a reconciliation check is falsifiable on your document, every time. It changes what a conversion means: not "here are some numbers we read", but "here are the numbers, and here is the proof they're complete." For the people putting those numbers into books they sign their name to, that's the entire difference. It's also, pleasingly, the same standard your accountant already holds you to — we just apply it about four seconds faster.

Try it on the ugliest statement you have — the dense one, the scanned one — at norekey.com. The balance check is exactly the kind of promise you should test before trusting.