I'm building a small tool that converts bank CSV files into .qbo files for QuickBooks (qbofile.com). When a generated file is wrong, QuickBooks rejects it with vague errors and the OFX spec doesn't tell you what QuickBooks actually checks. So I ran some experiments. Notes below, in case someone else hits the same wall.
The file is not XML
.qbo is Intuit's version of OFX 1.0.2, which is SGML. Leaf tags have no closing tag:
<TRNAMT>-42.50
<FITID>8f3a2b...






