It matters from the point the agreement is in force and from the date you make (or credit) the payment, because withholding tax is usually triggered at payment time, not year-end. YA 2026 is where many founders will feel the operational impact because those 2026 payments often flow into YA 2026 compliance and supporting schedules. The safest approach is to review Taiwan-linked payments before your first major 2026 payment run.