UK Tax Season 2026: Key Dates, Changes, and How to File

The UK tax season for the 2025-2026 tax year is underway, bringing with it important deadlines and considerations for taxpayers. With ongoing digital transformation initiatives and potential disruptions like civil servant strikes, understanding the current landscape is crucial for a smooth filing process. This guide provides an overview of key dates, recent changes, and resources to help navigate the system.

Key Dates for the 2025-2026 Tax Year

Taxpayers need to be aware of critical deadlines to avoid penalties. As of March 4, 2026, the deadline for filing Self Assessment tax returns is rapidly approaching.

• Self Assessment Filing Deadline: The deadline for online Self Assessment tax returns is nearing, with only eight days remaining as of January 23, 2026 .

Recent Changes and Updates

HMRC continues to implement changes aimed at streamlining the tax process and improving efficiency. Several key updates are relevant for the 2025-2026 tax year:

• Making Tax Digital (MTD): HMRC is encouraging taxpayers to choose the right software for Making Tax Digital for Income Tax, which is designed to modernize tax reporting.
• HMRC App: The HMRC app is available for mobile devices, providing access to tax information, National Insurance details, and benefits .
• Side Hustle Tax Rules: HMRC has launched a campaign to help individuals understand the tax implications of side hustles .
• Tax Code Changes: Your PAYE tax code may be affected by information provided in your tax return if received before December 31, 2025. It’s important to inform HMRC of any expected changes to amounts or claims in specific boxes to ensure your tax code is updated accurately .

Impact of Civil Servant Strikes

Digital traffic jams at the tax authorities are possible due to ongoing civil servant strikes. Taxpayers should be prepared for potential delays in processing returns and responding to inquiries.

Filing Your Tax Return

Taxpayers have several options for filing their tax returns:

• Online via HMRC: The most common method, accessible through the HMRC website.
• Through a Tax Agent: A professional tax advisor can assist with filing and tax planning.
• Paper Filing: While still available, online filing is generally faster and more efficient.

Tax Obligations for Government Entities

Government entities, including federal, state, and local governments, have specific tax obligations. While generally exempt from income tax under IRC section 115 when exercising public functions, they are still required to comply with employment tax regulations, including withholding federal income tax, Social Security, and Medicare taxes from employee wages . Section 218 agreements may too affect Social Security and Medicare withholding requirements for state and local governments .

Resources and Support

HMRC provides a range of resources to assist taxpayers:

• HMRC Website: https://www.gov.uk/government/organisations/hm-revenue-customs
• HMRC App: Downloadable for mobile devices.
• HMRC Helpline: For assistance with specific queries.

For those in California, the Franchise Tax Board (FTB) offers online services for filing, payments, and refund checks .

Key Takeaways

• The Self Assessment filing deadline is approaching quickly.
• Be aware of recent changes related to Making Tax Digital and the HMRC app.
• Potential delays may occur due to civil servant strikes.
• Government entities have unique tax obligations, particularly regarding employment taxes.