Do I need to declare my forex trading account to tax authorities?

Yes, most countries require declaring forex accounts and reporting profits/losses annually, even if no tax is due. FATCA and CRS agreements mean banks and brokers report to your home tax authority automatically for residents of 100+ countries. Undeclared offshore accounts risk fines or audits. US citizens must file FBAR for foreign accounts over 10k USD. Keep detailed records of deposits, withdrawals, and statements. Some jurisdictions require quarterly payments on estimated gains. Failing to declare invites penalties far exceeding taxes. Check your country's specific rules and reporting thresholds early.