Hi, Jarobiernacki.
To add bank details to your invoice, follow these steps:
1. Open the Gear icon, then select Account and settings.
2. Select Sales, and click the pencil for Invoice payments.

3. Add bank details or payment options in Payment instructions.
4. Click Save, then Done.

You can use the print preview or view the invoice as a PDF to check how the added bank details appear and make necessary adjustments if needed.

Feel free to reply below if you have further questions.