basically it wont let me do it but ive been asked for one from a contractor any hints?
This isn’t possible in Quick File. Is there any particular reason why you need a 100% discount invoice? There may be a better way of doing this.
i have been doing promo work with an established contractor who i put in regular tenders with, showing mu free promo time would be beneficial for there records and help me record when i am working for tax credit purposes/ hmrc 
I think it would be best to document this elsewhere. Zero value invoices don’t have any direct relevance in accounting so it’s not something we support.
I’m not sure about what kind of record keeping you require for claiming working tax credits but I doubt that you would need zero value invoices to support this? I have to confess I’m not an accountant so I’m not able to give you a categoric answer.
I’ve had occasions where I’ve wanted to have a nil invoice as well, but just create credit notes to get around it.
As Glenn says there’s no point in accounting terms in a record of a nil invoice. Might I suggest using an estimate in place of the invoice if the original intention is not to charge?
Steve Hills.