A simple contract with a foreign customer (primary document for tax reporting)?

Question

Law in IT

You need a simple direct contract with a client on Upwork (the order has already been completed) as a primary document for tax reporting, nothing more.
Requirements:
1. Bilingual EN-RU (two columns).
2. As little text as possible so as not to tire the client by reading (he absolutely does not need this contract). At the same time, obviously, the minimum set of essential requirements of such an international treaty should appear.
Questions:
1. How to reflect the fact that Upwork is used, and even takes 10% for itself.
2. Is it possible to somehow register the shortfall in foreign exchange earnings (this is for currency control) - with WireTransfer, there may be intermediary banks that steal their pennies, as a result, the declared amount will be slightly more than the incoming one.
3. Is a printout with the client's signature legally suitable for the tax office (so that he does not physically send the paper by mail)?
Where can I see an example / template of such an agreement? Thank you.

Answer 1

This is enough to pass the VC.
My post is not about this at all: "... the primary document for tax reporting ..." - think about it! What should I write in KUDIR in the column "Number of the primary document"?

Answer 2

OkScope.LONG_ACCESS_TOKEN