What QIF is
QIF is a plain text list of transactions, one field per line, each line beginning with a single letter that says which field it is. D is the date, T the amount, P the payee. A caret on its own line ends a transaction.
Quicken, and the long tail of banks and budgeting apps that still offer it because everything can read it.
What XML is
XML marks up data with nested named tags and optional attributes. It is verbose, strict about being well-formed, and can carry a schema that says what shape a document must have.
Enterprise integrations, government data feeds, RSS, SOAP services and older document formats.
What changes when you convert QIF to XML
Each block up to a caret becomes a row. Split transactions, which QIF writes as repeated S, E and $ lines, are joined into single cells rather than being spread across as many columns as the most-split transaction in the file has parts. The account type from the !Type header is added as a column.
Each row becomes an element with one child per column. Header names are rewritten where they have to be, because an XML tag cannot start with a digit or contain a space, so a column called 2024 Sales becomes _2024_Sales.
What carries over from QIF to XML
One property of the QIF has no home in XML, and it is worth knowing which before you convert.
QIF distinguishes a number from the text of a number; XML does not, so every value arrives as text and has to be re-parsed by whatever reads it next.