February 28, 2026: Q4 2025 VAT return due (60 days after Dec 31)
May 31, 2026: Q1 2026 VAT return due
June 30, 2026: Annual reconciliation completed (180-day "soft deadline")
August 29, 2026: Q2 2026 VAT return due
August 28, 2026: Final deadline for corrective returns for fiscal year 2025 (240 days after Dec 31)
November 30, 2026: Q3 2026 VAT return due
Plan backward from August 28 to ensure adequate time for reconciliation, discrepancy investigation, and corrective return preparation.
Late payment interest of 4% (2026) compounds daily from the due date until payment.
Example: You owe CHF 5,000 additional VAT from your 2025 reconciliation. Original Q4 2025 deadline was February 28, 2026. You submit corrective return and payment on June 15, 2026 (107 days late).
Interest owed: CHF 5,000 × 4% × (107 ÷ 365) = CHF 58.63
Not devastating for CHF 5,000, but scales quickly for larger amounts or longer delays.