BASALT · JOURNAL
How to redact bank account numbers in a PDF
Bank documents repeat identifiers by design. An account number may appear in the statement header, transaction description, remittance slip, check image, barcode, filename, and an attached spreadsheet. Review the document as a container, not a stack of visible pages.
Build a pattern list
Search the full account number, masked versions, last four digits with surrounding labels, and groups with spaces or hyphens. Search account, acct, routing, ABA, IBAN, and SWIFT to locate values OCR may have misread. Do not blindly redact every long number: transaction IDs and check numbers may need to remain.
For checks, review MICR lines and check images visually. Those numbers can be image pixels rather than searchable text. Barcodes and QR codes may encode payment or account data and require scanning or full image-region removal.
Preserve useful financial evidence
Mark only the approved identifier where possible. Dates, transaction descriptions, and amounts may be essential to the reader. After applying redactions, reconcile opening balance, activity, and closing balance with the approved source so an oversized image mark has not destroyed figures beside the account number.
Check forms and attachments
PDF forms can keep entered values in a field dictionary independently of the visible appearance. Remove the stored value; flattening alone is not enough. Inspect and remove or separately process attached CSV, OFX, or spreadsheet files.
Export a new release copy and independently search it for every pattern. Inspect metadata and old revisions, then confirm the output opens without exposing a thumbnail of the original page.
Frequently asked questions
Should I redact the routing number too?
That depends on the purpose and policy. A routing number identifies a bank rather than one customer, but it can still be sensitive in context. Follow the disclosure instruction rather than assuming.
Why does the number still copy after I covered it?
The covering shape changed only the page appearance. The text object underneath is still present and must be removed from the content stream.
Can a PDF contain the original statement as an attachment?
Yes. Embedded files are independent of the pages and must be inventoried and removed or redacted separately.
Doing it in Basalt
Basalt finds repeated account-number patterns locally, destroys text and image content, clears form values and embedded files, and verifies the output before writing it. Nearby unmarked text is also checked for survival. Get 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.