It's important with any business you come up with a revenue recognition strategy.
Use the "Invoices" tab in Firmhouse to export invoices, and use that as method to do revenue recognition and tax registration for your own bookkeeping.
What's important to note at this point is that a refund that is triggered will not automatically also generate a credit invoice for that payment. As such, whenever a payment is refunded, someone needs to make sure there's also a credit invoice generated for the refund.
To generate a credit invoice for the full amount, click the button in the upper right corner when viewing the original invoice you want to credit.
If you only want to refund a part of the invoice, go to the subscribers overview page and select the "Payments & Invoices" submenu.
In the Invoices menu there is a "Create Invoice" button.
For a (partial) refund, enter the amount to invoice with a minus sign (so -5.00 for 5 euro credit).
We recommend a scheduled bookkeeping moment, where you can check for refunds and generate any credit invoices at that moment.