With Holvi, you can create and send invoices in an easy and fast way. Learn more how to set up invoices here.
The invoicing tool will link incoming payments automatically to invoices with the reference number. If the payment was carried out with or without an incorrect reference number, it will not be automatically linked to an invoice.
You can mark the invoice as paid manually. In order to do so, the payment you wish to link with the invoice has to be in the income category "uncategorized". If this is the case, you can simply go to your invoice and select "Mark as" and then "Paid".
More information on the usage of the invoicing tool can be found here.