QBO file format explained.

Older QBO files commonly use an OFX 1.x SGML-style header followed by an <OFX> body. Newer OFX variants may use XML. A parser should inspect the structure instead of relying only on the extension.

OFXHEADER:100
DATA:OFXSGML
VERSION:102
ENCODING:USASCII
CHARSET:1252
COMPRESSION:NONE

Bank statements commonly use BANKMSGSRSV1, STMTRS, and BANKACCTFROM. Credit-card statements may use CREDITCARDMSGSRSV1, CCSTMTRS, and CCACCTFROM.

<STMTTRN>
<TRNTYPE>DEBIT
<DTPOSTED>20260710120000.000[-5:EST]
<TRNAMT>-24.75
<FITID>FICTIONAL-0001
<NAME>Fictional Supply Store
</STMTTRN>

A QBO header declares an encoding. BankFileKit's beta writer declares USASCII with character set 1252 and replaces non-ASCII characters with ?. Review names and memos when the source contains accented or non-Latin text.

The file normally carries bank-feed transactions, not invoices, chart-of-accounts rules, reconciliations, payroll, or an entire QuickBooks company. See the QBO definition guide for the distinction from QBW files.

The current reader extracts bank or credit-card transaction blocks with valid dates and amounts. It does not promise support for every OFX message set, investment statement, loan statement, or vendor-specific extension.

The CSV/XLSX to QBO writer creates a candidate US English and USD Web Connect file. It has not been verified in real QuickBooks Desktop, so users must test a fictional file in a blank company.

A structurally plausible QBO file can still fail because the target product, account connection, institution fields, or transaction identifiers are incompatible. Successful download is not proof of successful import.