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Understanding Excel workbook

XLSX is the Excel workbook format, standardised as ECMA-376 Office Open XML. Compare bank statements in XLSX and CSV and see what Klarbon writes.

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XLSX is the file format of Excel workbooks, standardised as Office Open XML in ECMA-376. A file is a zipped set of XML parts: the workbook, its sheets and their styles. Unlike CSV, it stores dates as dates and amounts as numbers, so a spreadsheet opens a statement without guessing separators or date order. Klarbon writes bank statements as XLSX.

What is in an XLSX file?

Part Holds
xl/workbook.xml the workbook and its list of sheets
xl/worksheets/sheet1.xml the cells of one sheet
xl/styles.xml number and date formats, fonts
[Content_Types].xml what each part is

The format is published by Ecma International (ECMA-376). Use spreadsheet software that supports Office Open XML.

What does Klarbon's Excel statement hold?

One sheet with a header row and one row per transaction: booking date, value date, amount, currency, counterparty, counterparty IBAN, description, reference and, where the statement shows it, the running balance. Dates are real dates, amounts are numbers with their sign, and the header row is frozen with a filter. Column names are in English.

When should I use XLSX?

To check, sort or total the transactions yourself, or to hand them to someone who works in a spreadsheet. For accounting imports, use the format your software specifies, such as CSV, CAMT.053 or MT940.

Frequently asked questions

Is XLSX better than CSV for a bank statement?

For reading and working with the figures, yes. Dates and amounts are stored as real dates and numbers, so nothing depends on your computer's separator settings. For a software import, use the format the import screen names.

Can accounting software import XLSX?

Use XLSX only if your software's import instructions explicitly support it. Check the required columns and cell types before importing.

Does an XLSX file lose any precision?

Excel keeps 15 significant digits. Klarbon refuses to write an amount it would have to round, rather than change your figures.

Sources

Updated 5 November 2026