Every conversion is verified against the statement itself before you ever see an export button.
The check
A bank statement declares its own ground truth: an opening balance and a closing balance. After extraction, NoRekey sums every transaction amount and checks that opening + all transactions = closing, to the penny. Only a statement that passes is tagged balanced.
Why it matters
Extraction mistakes in this category of tool are rarely random noise — they're a dropped row, a flipped sign, or a misread decimal. Every one of those breaks the arithmetic, so the balance check catches exactly the errors that matter to bookkeeping.
What "needs review" means
If the rows don't reconcile, the conversion is clearly flagged — in the converter, and in your history. You can still open and export the data (it's often fine except one identifiable row), but you'll know to compare against the original before importing. Nothing unbalanced is ever exported silently.
When the check can't run
Some statements don't print an opening or closing balance — certain card statements and exports omit them. In that case there's nothing to verify against, and the conversion completes without a balanced tag rather than pretending to a guarantee it can't make.