Hi Mathilda
In order for AccountRight to use a particular customized form for a sale, the form and the sale need to be of the same type. So if the customized form is a time billing form, but the sale is a service type sale (for example) then when the sale is printed or emailed it will use whichever service sale form has been selected in the Print / Email Invoices >> Advanced Filters for the Sales type of ‘Service”
So if you were wanting to use a Time billing customized form you would need to ensure that the sale was recorded as a time billing type of sale, not a different type