If you don't want your bank details to be displayed on all your invoices, then you can add them to a single invoice.
In the Web Portal to go CRM > Invoices > select the Invoice > scroll down to Notes > Enter Bank Details > Save at the bottom of the invoice.
In the App go to > Accounts > Invoices > select the Invoice > scroll down to click Add Note > Enter Bank Details where is says 'Content' > Add Note.
When you send the invoice, the bank details that have been added will be viewable by your client.
If you would like your bank details added to all invoices: