Idk about other countries, but in Poland you need special VAT invoice that mentioned your company by name and tax id. Regular receipts don't have that.
In certain jurisdictions only documents signed with the blood of firstborns will do. O, and please dont forget the stamps. All of them. O, and make sure the initial of your second name isn't missing, otherwise you might well be someone entirely different and we couldn't even think of processing the request.
And that's just to get reimbursed, for tax purposes we have an extra set of requirements. Of course.