Hi LindyMH
That does sound odd, AccountRight does break long transactions onto additional pages automatically if the first page can't fit it all. I'd suggest try printing the invoice/send it to disk using one of the AccountRight default forms, if that breaks up the invoice to multiple pages correctly, please do review the set up of the custom form used via Setup > Customise Forms > Invoices. Alternatively, you can consider rebuild the custom form from the default forms, as the custom form could get corrupted.
Please feel free to let us know how you go or if you have any further questions.