Am I able to use 8.5 x 5.5 paper for invoicing?

You can use any paper size, louisahadden.

You can select the size of the paper you'd like in printing invoices or any sales transactions. When printing invoices, on the Print page, choose your preferred paper size from the Paper size drop-down. 

For more information, check how to print sales forms.

I'd be glad to help you if you have other concerns. Have a great day!

Thank you for your reply.

I just tried 1 invoice and when I printed it it has not included the whole invoice, it has cut off everything after the tax box.

Any other suggestions on how to get my invoices on 8.5 x 5.5?

Louisa