Taking on international clients opens up real revenue, but it raises questions about work authorization, tax withholding, and cross-border payment that are worth understanding before you sign anything.
Where you're physically located is what matters, not where the client is. If you're working from your home country for a client based elsewhere, you generally don't need a work visa for the client's country, your work is treated as an export of services. That changes the moment you travel to the client's country to work on-site, a standard tourist visa almost never covers "productive labor," even if you're being paid from abroad.
Tax withholding. Some countries require companies to withhold a percentage of payments to foreign contractors unless a tax treaty applies. Ask the client to file the relevant treaty form (for example a W-8BEN for US-based clients) to reduce or eliminate that withholding, and confirm with a tax professional that you're not being taxed twice on the same income.
Getting paid. Traditional wire transfers are slow and expensive. A dedicated international payment processor or multi-currency account, converting at the mid-market rate, keeps more of what you invoice. Spell out in the contract which currency you're invoicing in and who absorbs transfer fees, and see the currency hedging risk calculator for how much a payment delay could actually cost you in exchange-rate movement.
Contract basics. Specify the governing law and jurisdiction, ideally your own, since enforcing an unpaid invoice internationally is often not worth the cost. Favor larger upfront deposits or milestone payments over a single end-of-project payment, and use a proper contract either way.