I freelance for clients in three countries and live in a fourth. Tax feels like a minefield and I'm terrified of being taxed twice. How did other freelancers get a handle on where you actually owe what?
The concept that unlocked it for me: tax residency. Figure out where you're tax-resident first, then the rest hangs off that. Once I understood that, the double-tax fear shrank a lot.
Get an accountant who works with cross-border cases — not the one who does local returns. Double-taxation treaties exist specifically to stop you being taxed twice, but you have to claim them right, and the good ones save you more than they cost.
I kept a simple log of days in each country from day one. Sounds paranoid; turned out to be exactly what the accountant needed and what residency often hinges on.
Tax is the area I'd most strongly say: don't take numbers or "you'll owe X" from a forum, mine included. Thresholds, treaties and residency rules are country-specific and change. The Taxes section of your guide is a primer, but for a multi-country freelance setup a cross-border accountant is genuinely worth it — this is where DIY bites hardest.
"Figure out residency first" + "log your days from day one" — that's the two things I was missing. Booking an accountant this week.