BASALT · JOURNAL
Redacting financial statements and bank records
Financial documents are produced constantly in litigation, lending, audit and divorce, and they carry a specific hazard: the same number appears many times in different formats.
What comes out
Full account numbers, sort codes and routing numbers. Card numbers. Counterparty names where they are not relevant to the matter. Balances, where only transactions are in scope. Addresses and identifiers of third parties appearing in transaction descriptions.
Why partial masking fails
Showing the last four digits is standard practice and it assumes the rest is unavailable elsewhere. In a document set it frequently is not.
The same account can appear in full on a covering letter, a payment instruction, or a scanned cheque image later in the same production. Masking it on the statement while leaving it complete three hundred pages later achieves nothing, and nobody notices because the two pages are never read together.
Search the whole set for the number rather than redacting page by page.
Statements are usually scans
Bank statements arrive as scanned images more often than as native text, which changes the work entirely. There is no text to remove, so redaction means destroying pixels and re-encoding the image.
If the set has been OCRed to make it searchable, and it usually has, there is now an invisible text layer as well. Destroying the pixels while leaving that layer intact produces a document that looks redacted and remains fully machine readable.
Both layers must be handled, and the only way to know is to extract text from the finished file and search it.
Totals and derivation
A redaction that removes individual transactions but leaves a total lets anyone compute what was removed, particularly if only one or two entries are missing.
This is a genuine and frequent failure. If the totals remain meaningful, either recompute them or remove them too.
Before producing
Check the metadata. Statements exported from banking software often carry the account holder's name and sometimes the account number in document properties, entirely separately from anything on the page.
This is a description of common practice rather than legal advice. Obligations vary by jurisdiction and by the terms you are working under, and the authority that governs your work is the one to check with.
Frequently asked questions
What should be redacted from bank statements?
Full account, sort code and routing numbers, card numbers, irrelevant counterparty names, balances where only transactions are in scope, and third party identifiers appearing in transaction descriptions.
Is showing the last four digits of an account number safe?
Only if the full number appears nowhere else in the document set. In practice it often appears complete on a covering letter or a scanned cheque elsewhere in the same production, which defeats the masking entirely.
How do I redact a scanned bank statement?
The words are pixels, so the image must be decoded, the pixels destroyed and the image re-encoded. If the set was OCRed the invisible text layer must be removed too, or the document stays machine readable while looking redacted.
Can redacted financial figures be worked out from totals?
Yes, frequently. If individual transactions are removed but a total remains, the missing amount is simple arithmetic, particularly when only one or two entries are gone. Recompute or remove the totals as well.
Doing it in Basalt
Basalt is a native macOS PDF toolkit built around redaction that removes content rather than covering it. After writing a file it re-opens its own output with an independent parser, searches for the material again, and refuses to save if anything is found. It also strips metadata, XMP, attachments, embedded scripts and hidden layers as part of the same operation, and a separate Inspector reports what any PDF still hides, including documents Basalt did not create. Everything runs on your Mac: the engine holds no network entitlement at all, which macOS enforces at the code-signature level. A one time $29 licence covers up to three Macs, free for the first 24 hours. basaltformac.com, or brew install --cask chipmunk1101/tap/basalt.
Redaction that proves itself
Basalt destroys the content you mark, then re-opens the file it wrote and proves the content is gone before it saves anything. Your documents never leave your Mac.