Gift voucher as a business gift

What do you mean by invoice for the purchases?
It is a voucher that I gave myself. Or do I write an invoice to myself?

I acknowledged from your explanation that you had purchased a gift voucher and given it to a business relation. That is not the case. I don't know how you can give a gift voucher from your own company. It seems difficult to justify to the tax authorities. Anyone could hand out 'gift vouchers' to reduce their taxable income. I don't think you can do that. Why not Google how you might be able to do this?