Can anyone help plse - Best way to attach an online form to a transaction record?

Hi,

I'm trying to figure out the best way of doing the following and would appreciate if anyone can point me in the right direction;

We sell some items which when bought by a private individual can be supplied without charging them tax. To do this we need them to complete a basic declaration stating that they are buying them for their own personal use or the use of another private individual. The simplest way we can think of doing this is by letting the customer place their order as normal and then going to an online form and completing the declaration. We will make the adjustment to the tax manually when we have received their notification. The form only needs some basic fields on