Before submitting content I'd like to know a few things. If I choose Collected by itch.io, paid later, do I need to have a trade certificate in my/my company's country of residence? Am I obliged to pay any tax from what is paid to me by itch.io with this payout model chosen? Are the input tax credits from collected VAT yours or mine/my company's to keep with this payout model? I want to do business from Slovak Republic.

Generally speaking, money you get from itch.io is counted as income, so you'll be responsible for income tax if your country has it. I can't speak for the legal requirements of selling goods through a US company for your country, so I recommend consulting a professional. We are the merchant of record with our "paid later" system so we would be responsible for tax on the sale, VAT.

Thanks.