A downloaded exchange file is a starting record, not a finished history. Dates may use different time zones, quantities may appear in separate columns, and one transfer can show up in more than one export. Organise the file in stages so every correction remains traceable. This workflow prepares records for review; it does not determine tax treatment or reconstruct missing facts.
Preserve the original first
Keep an untouched copy with the service name, covered date range and download date. Work on a separate copy. If you later discover a field was interpreted incorrectly, the original gives you something to return to. Renaming columns in the only copy makes it harder to tell which wording came from the service and which came from your own interpretation.
Create a source register for every imported file. Record its filename, account label, export type and any stated time zone. Use neutral account labels rather than credentials. A transaction-history export and a balance snapshot are different kinds of evidence; do not combine them as if they were interchangeable lists of events.
Map fields before combining rows
Identify the date, event type, asset, quantity, fee asset, fee amount and reference fields where present. Check whether outgoing quantities are negative or represented by a separate event type. Keep currencies and units explicit. A number such as 12.50 cannot be interpreted safely without knowing whether it means asset quantity, fiat value or a fee.
Use five fictional rows to test your mapping before importing a large history. Include a purchase, a disposal, a transfer, a fee and an incomplete entry. Inspect the resulting fields rather than only checking whether the import reports success. A file can load without errors while placing the wrong column in an important field.
Treat duplicates as candidates
Overlapping exports can contain the same event twice, but matching quantities do not prove duplication. Two recurring purchases may legitimately have the same amount. Compare references, timestamps, account labels, networks and event types. Keep a review queue for uncertain matches instead of silently removing every similar-looking row.
Transfers need another distinction. An outgoing row from one account and an incoming row at another can describe two sides of one movement. Preserve both source records while recording the possible relationship. Fees, timing differences and incomplete references can complicate a match. If the evidence is insufficient, leave the relationship unresolved rather than forcing the totals to agree.
Make the exception list part of the output
List missing dates, unknown assets, unexplained fee currencies and unmatched movements separately. Assign each issue a source file and row reference. “Missing acquisition record for this quantity” is more useful than filling the cost with zero. A blank fact is not a zero-valued fact, even when a later calculation would be easier with a number.
Export the organised records with the source register and exception list. If someone else will review them, explain which fields were mapped, which rows were excluded as confirmed duplicates and which assumptions remain. Keep the original files available in the appropriate protected location. A successful cleanup does not hide the messy parts; it makes them identifiable and gives the reviewer a route back to the evidence behind each row.
Transaction Ledger Organizer helps you organise your own notes in this browser. Keep credentials and recovery material out of your project.