The tax treaty
None
The United States has no income tax treaty with Serbia. Dividends, interest and royalties from US sources are withheld at the standard 30%. Money you earn for work you do in Serbia isn't US-source income, so nothing is withheld on it.
Stripe
Not available locally
Stripe doesn't take businesses registered in Serbia. A US LLC with an EIN and a US bank account is a US business, so it can apply for a US Stripe account, and that's often the main reason founders in Serbia form one.
Banking
Mercury available
Mercury opens accounts remotely for US companies whose founders live in Serbia. It asks for the EIN, the formation documents, your passport, a real business address and a description of the company's existing or planned US operations. Relay asks a non-US owner for a US address, an ITIN or Social Security Number and a US operating presence, so it rarely suits a founder living in Serbia.
The time difference
UTC+2
New York is 6 hours behind Serbia in summer. Everything we do is in writing, through your dashboard and email, and we reply within one business day, so the time difference rarely slows anything down.