A credit note follows the same path in Kasklaar as an invoice: recognise, booking proposal, approve, book. The difference is the sign: the amounts are negative. If an invoice is already booked and something still turns out to be wrong, you adjust it in your accounting package; Kasklaar then picks up the correction.
Your agents read the document type from the document itself: if it says "Creditnota" or "Credit note", or arrives as an e-invoice of the credit note type, it is one. A negative total alone does not make a document a credit note. If you see it set wrongly, choose Credit note at the top under Document type; the amounts flip along.
A credit note is negative in Kasklaar. If extraction reads the lines as positive, Kasklaar flips everything: header, lines and VAT. If there are plus and minus lines, for example a partial credit with a settlement, Kasklaar leaves the amounts as they are and says so with the notice Credit note with mixed signs: check the lines before approving.
If the sign of the header amounts does not match the lines, Kasklaar corrects the header and reports it. That notice also asks for a look from you.
Ledger account, VAT code and VAT scenario are chosen the same way as for an invoice; on a reverse-charged credit note the two VAT rows flip along. When matching to the bank, Kasklaar looks for a receipt instead of a payment. To your accounting package the credit note goes as a purchase entry with negative amounts, in the same journal as your invoices.
Kasklaar does not link a credit note to the original invoice. If you want to record that relation, put the invoice number in the description.
As long as an invoice is not yet approved, you change everything on the booking proposal. After that it is fixed and gets booked; in Kasklaar it is then Completed.
If something is wrong with a booked invoice, you have two routes. If the supplier sends a credit note, you simply process it in Kasklaar; it books the amount against the invoice. If the mistake is in the booking itself, a wrong account or VAT code, you correct that in your accounting package. Kasklaar picks up that correction in the list of booked invoices; the completed booking proposal keeps showing the original version.
Under Failed you see why. After a failed processing, Retry resumes the step that went wrong. After a failed booking, read the reason, fix it in your accounting package and click Retry. If you cannot resolve it, close the invoice with Close invoice; it will then not be booked.
Kasklaar reports the credit note as a possible duplicate. Because the invoice number on the credit note is often that of the invoice. Resolve the warning with the thumbs-up; see How the duplicate check works.
There is a discount on a line, is that a credit note? No. Kasklaar reports "A credit of … is already in this amount" on the line; the document stays an invoice.
Your agents got it wrong. Tell us, every time. Click the speech bubble at the top right of the invoice, Give feedback, and describe what went wrong; we look at it and use it to improve processing. Correct the invoice yourself as well, so it is right straight away.