How do I add my bank details on my invoice

We can the bank details by customising the form, alan-synopsis1-c.

Let me guide you with these steps:

1. From the Gear icon, select Custom form styles.
2. Locate the invoice template, and then click Edit.
3. Go to the Content tab.
4. Click the footer section.
5. Add your bank information on the Your payment details field.
6. Click Done.

I've also added this screenshot as your reference:

If you want to create your own invoice template, you can import a style. Here's an article for more information: Import Custom Form Styles For Invoices or Estimates.

I'll be around if there's anything that I can help. Have a good day!