2026 International Tax Calendar
Filing deadlines, regime windows, and policy implementation dates for cross-border tax planning in 2026. Curated by TaxAtlas Editorial — verify exact dates with the relevant tax authority before relying on any item for filing or election decisions.
December 2025
US TCJA individual provisions scheduled sunset (watch 2026 legislation)
Many 2017 Tax Cuts and Jobs Act individual provisions (bracket structure, standard deduction, estate exemption, QBI) sunset at end of 2025. Congressional action through 2026 will determine extension vs reversion.
January 2026
- medium impactPolicyJanuary 1, 2026Global (OECD)
Pillar Two next-tranche implementations
Several remaining jurisdictions (smaller financial centres, additional emerging economies) implementing Qualified Domestic Minimum Top-up Tax from 1 January 2026. Verify status by jurisdiction for in-scope MNEs.
- high impactPolicyJanuary 1, 2026Global
CARF (Crypto-Asset Reporting Framework) rollouts
Multiple jurisdictions implementing the OECD Crypto-Asset Reporting Framework in 2026 — automatic exchange of crypto-account information between tax authorities. Affects all material crypto holders cross-border.
March 2026
Portugal IFICI registration window — typical Q1 deadline
Qualifying inbound residents for the IFICI / NHR 2.0 regime register through the Portuguese tax authority. Specific role / activity eligibility must be confirmed before registration.
April 2026
FBAR (FinCEN 114) for 2025 due
US persons with aggregate foreign accounts ≥$10,000 at any point in 2025 must file. Automatic extension to October 15, 2026.
US Form 1040 for 2025 tax year due
Standard US federal tax filing deadline. Automatic extension to October 15 with timely Form 4868. US citizens abroad get an automatic 2-month extension to June 15.
Singapore individual income tax return due
Singapore individuals must file form B / B1 by 15 April (paper) or 18 April (e-filing). Tax residents file on Singapore-source income (worldwide if not on territorial relief).
June 2026
US citizens abroad — automatic 1040 extension deadline
US citizens and residents who were abroad on April 15 get an automatic 2-month extension to file (not to pay). Form 4868 by this date for further extension to October 15.
September 2026
UAE corporate tax — typical first-year filing window
UAE corporate tax returns are due 9 months after the financial year-end. For taxpayers with a December year-end, this puts the deadline at 30 September following the tax year.
October 2026
FBAR + 1040 extended deadline
Final extended deadline for 2025 US Form 1040 (Form 4868 filed) and FBAR (automatic extension). No further extensions available.
November 2026
Italy flat tax — typical first-year election deadline
Italian residents electing the €200,000 HNW flat-tax regime typically make the election in their first Italian tax return, due 30 November of the year following the tax year. Earlier interpello recommended.
January 2027
UK self-assessment for 2025/26 tax year
UK self-assessment for the 2025/26 tax year (6 April 2025 to 5 April 2026) is due by 31 January 2027 online. First year under the new FIG / non-dom regime.
April 2027
UK TRF 12% window — final year at 12% rate
Temporary Repatriation Facility: remit pre-April-2025 foreign income and gains at 12% for the 2026/27 tax year ending 5 April 2027. Rate rises to 15% for 2027/28.
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Dates are best-effort summaries. Tax authorities can and do change deadlines; some dates depend on the taxpayer\'s specific year-end. Always confirm with the relevant tax authority or a qualified professional before relying on any item for filing, election, or planning decisions. Not tax advice.