Storno a posted journal entry: post its mirror image (accountant role).

Nothing is deleted; the original stays, linked both ways, and the reversal entry is returned. The only VAT-correct storno door — VAT postings, open items and what the document spawned are all unwound.

body.posting_date dates the reversal and decides its period; omitted, it reuses the original's date and period.

Refusals, in evaluation order — 409 when: the entry is itself a reversal (post a new correcting entry instead); the reversal date falls in a filed/paid VAT period (date it into an open one); an open item still carries a live settlement (unlink or reverse the payment first); or — only with posting_date — its period is closed, its fiscal year sealed, or no fiscal year covers it.