What
MT940 is a SWIFT message that reports a customer's account statement. Banks send it as .sta, .swi, .mt940 or .txt. Statement lines sit between tags such as :61: for a transaction and :86: for narrative.
Unlike BAI2, MT940 has no control-total trailer. The check that matters is opening balance plus net movement against the closing balance the message itself states.
Why
A raw MT940 is not a spreadsheet. Pasting it into Excel leaves tags in cells and splits narratives across rows. You cannot reconcile a SWIFT message until each :61: line is one transaction with its :86: narrative attached.
How
Drop the file on the MT940 converter. It writes one spreadsheet row per transaction and checks opening plus net movement against the closing balance in the message. Download CSV or Excel. You do not need an account.
Then check statement quality and reconcile to the cash book. Load the synthetic sample on the converter if you want to see the run first.