An invoice must have a positive total amount, and every line must use a positive price. This follows the European e-invoicing rules: on the Peppol network, a correction or reimbursement may not be sent as an invoice with a negative amount. It must be sent as a credit note, a separate document type with a positive amount.
Adding a negative line to an invoice
A price cannot be negative on Billtobox. If you need a line that reduces the invoice total, for example for returned goods, a deposit, or a discount, enter a negative quantity with a positive price instead.
Example: for returned goods worth 4.50 euros, do not enter -4.50 as the price. Enter a quantity of -1 and a price of 4.50. The line total is then -4.50, and the invoice remains valid as long as the total amount of the invoice stays positive.
Correcting or refunding an invoice
If you need to correct or (partially) refund an invoice you already sent, do not create a negative invoice: create a credit note for the amount to be corrected. See How do I create a credit note?
Received a document with negative amounts?
E-invoices exchanged via the Peppol network cannot contain a negative total amount; the network rules prevent them from being sent. If a supplier still provides you with a document containing negative amounts in another way, ask them to send a correct invoice, or a credit note if they owe you money.
Checking the type of a document
You can check the type of any document on its detail page (click the document in the list), on the Document type line.