As you know you can claim costs for your business so you only have to pay tax on your business profits. E.g. When you buy advertising. I want to give a prize away on my site and as this will be a business cost, I want to know how to prove this as a tax expense without an invoice. Can anyone help?
Yes it should be enough, especially for a small thing like that. As long as you have some sort of record that proves it the tax authorities should be happy. As to the deductibility of it, that I don't know, unless you know you should probably ask a tax advisor