Correcting an e-invoice: cancellation invoices in Germany
A sent invoice isn't changed or deleted. It's corrected with a new document that refers to the original.
The rule
Once an invoice is with your customer, you don't edit it. You issue a new document that refers explicitly to the original (its number and date). With e-invoices, that document must be an e-invoice too.
The cancellation invoice (Stornorechnung)
It takes the original back completely: the same lines with the signs reversed, its own new number, and the reference to the original. In the e-invoice it's document type 384 (corrected invoice) with the preceding-invoice reference. If the work is still to be billed, a new, correct invoice follows.
Not a "Gutschrift"
In German VAT law a Gutschrift is something else: an invoice your customer issues on your behalf (self-billing). Don't call a cancellation a Gutschrift: it causes confusion.
When no correction is needed
If only the amount paid changes, for example an early-payment discount, no new invoice is needed; it's recorded in the bookkeeping.
With Filekin
In Filekin for Business, open the invoice and choose "Cancel or correct". Filekin makes the cancellation as a valid e-invoice with a new number and the reference to the original, and can open the corrected invoice straight away. Check any e-invoice with the validator.