How to merge multiple bank statements into one file

When to merge, and when not to

The case against merging for accounting imports is duplicate control. Software matches on periods and transaction ids; one large file spanning a year makes it harder to re-import a single month later without doubling it up.

Check each statement before combining

A merged file inherits every problem of its parts, and hides them better. Verify each conversion individually first.

• Each statement reconciled: opening plus credits minus debits equals its own closing balance.
• The row count matches any count the statement prints.
• The dates fall inside that statement's period.

The Conversion Report for each statement records exactly this. A statement flagged for review before merging will still be wrong afterwards, just harder to spot among a thousand rows.

The joins are where errors hide

When several statements are stitched together, the seams deserve attention that the middles do not.

1. Sort by date and read the rows either side of each month boundary.
2. Check that one statement's closing balance equals the next one's opening balance. If it does not, a statement is missing from the middle of the sequence.
3. Look for the same transaction appearing twice around a boundary. Statements sometimes list a transaction dated on the last day of one period and posted in the next.
4. Confirm no month is absent. Twelve statements should produce twelve period boundaries, not eleven.

The closing-to-opening test is the strongest one available: it proves there is no gap, using figures printed by the bank rather than anything derived.

Merging here

Batch upload and merging are available on paid plans. Upload the statements together, let each one convert and be reviewed, then export them as a single file. The rows are ordered chronologically across the whole set rather than concatenated file by file.

• Rows keep the account they came from, so a merged export of two accounts can still be split later.
• The per-statement metadata — institution, period, account number — is preserved rather than flattened away.
• Each source statement is still checked on its own, so a problem is attributed to the statement it came from.

On the free plan, convert each statement separately and combine the CSVs yourself. Keep the header row from only the first file.

Combining exports by hand

If you are stitching files together in a spreadsheet, a few habits prevent the usual mess.

• Add a Source column naming the statement each row came from before you combine anything. It costs nothing and makes every later question answerable.
• Combine the raw exports, not files you have already edited, so the process can be repeated.
• Sort by date only after everything is in, and check that the sort is by real dates rather than text. Dates as YYYY-MM-DD sort correctly either way.
• Do not carry the balance column across a merge of two accounts. A running balance means nothing once two accounts are interleaved.

If dates or amounts misbehave when the files open, Excel's CSV handling is usually the cause rather than the export.

Checking the merged file

Two arithmetic checks confirm the merge did not lose or duplicate anything.

• The sum of all credits and all debits across the merged file should equal the sum of the individual statements' totals.
• The first statement's opening balance, plus every transaction in the merged file, should equal the last statement's closing balance.

That second test is the whole year in one line, and it is the one worth keeping alongside the file as evidence the set is complete.