Tut / Brucanna,
Please I need your assistant on our sales invoice.
I want the bank details to be on our sales invoice such that it prompts up once a new sales invoice wants to be raised.
See existing attached invoice:
until you find a programmer you can show the necessary details with a custom field which will appear at the bottom of sales invoices. if you need to show your bank details below the customer address, then you can also temporarily insert the details in the customer address field below their address.
as explained earlier, you will have to hire someone locally to modify the theme as per your preferences.
you can set the custom field to show as a default for all sales invoices. read the guide on Form Defaults.
if you are looking to change how the data is presented on the sales invoice, then you have no other option than developing a custom theme.