To handle reminder fees on an unpaid invoice, bexio offers two options: issue a separate invoice for the fees while keeping the initial invoice in "Overdue" status, or revert the original invoice to "Draft" status to add a fee line item directly before re-issuing it with its original date. However, this second method requires that the relevant fiscal year and VAT period have not yet been closed. In all cases, please verify the appropriate method, accounting treatment, and applicable VAT rate directly with your fiduciary, as bexio does not provide tax advice.