After an order you will receive an email with a link to a pay gateway.
On that page you can fill out the amount that is stated on the invoice AND below that you can add a message, that is where you add the invoice number.
When you click next you will see an array of payment options like iDEAL and BankContact but also for debit and creditcard.
Once you made your payment we will manually review your payment and if accepted we will set your invoice to paid.
This process can take upto 24hours, if you have not received a confirmation that the invoice has been set to paid, please contact our support.