If you have ever looked through your financial documents in the United Kingdom and questioned why the tax year starts on April 6, then you are not the only one. The most logical solution for countries to start their tax year is from January 1, or in accordance with their financial year. 

This has made people highly curious about the tax year dates of the United Kingdom, and you will be surprised to know that the nation has not chosen this date randomly; rather, there is a practical explanation for the same, which is not very difficult for people to understand. 

This guide talks all about the origin of this unusual date and the different historical events that have shaped it. So, get ready to understand this odd tradition that is still influencing the UK tax administration today. 

Shift from the Julian Calendar to the Gregorian Calendar 

Understanding the beginning date of the UK tax year calls for a return to the Julian calendar, created by Julius Caesar in 45 BCE. In this framework, March 25 marked the New Year, a day with religious and political significance all around Europe. Among the "quarter days" in England used to settle rents and invoices, Lady Day fell on the Feast of the Annunciation in the Christian calendar.

From at least the 12th century until 1752, 25 March signalled the formal beginning of the new legal year in England. For example, the year 1700 officially started on March 25, 1700, and ran until March 24, 1701. However, a major turning point came when the Julian Calendar and the actual solar year started experiencing discrepancies. 

By the 18th century, the Julian Calendar experienced a difference of 11 days when compared to the solar year, and this created confusion and discontent among the common folk. As a result, Britain shifted to the Gregorian Calendar, which was already used by the rest of the continent by then. 

The Calendar Reform of 1752

With the adoption of the Gregorian Calendar, the United Kingdom experienced a difference in dates, as September 2 was directly followed by September 14. 

• The start of the legal year was officially changed from 25 March to 1 January (from 1752 onwards).

• However, fiscal and administrative systems still tied to the old calendar needed adjusting.

The loss of days was not appreciated by the treasury of the United Kingdom, which is why steps to taken to fix it. To avoid the loss of revenue, the treasury changed the UK Tax Year date from 25 March to April 5. 

The final change to the date happened in 1800 when the tax date was shifted once again from April 5 to April 6, to correct an error made by the leap year. 

Exploring the Practical Reasons For Sticking with April 6 For Tax Administration 

Although it seems strange, the UK government has never changed the tax year to start on January 1 for good cause:

• Institutional continuity: Hundreds of years of bureaucratic systems, accounting methods, and legal structures have been built around the 6 April starting date.

• Avoiding overlap: The tax year should not be changed to January 1, as it may overlap with the Christmas and New Year holiday season, hence complicating pay and filing procedures.

• No strong incentive: Despite the obvious need to change the date, the costs and effort associated with reorganising tax systems—both public and private—have outweighed the benefits.

Who should be familiar with the UK Tax Year Dates?

Knowing the UK tax year dates is essential for a wide range of individuals and organisations, especially those involved in financial planning, compliance, and reporting. Here’s a breakdown of who should be aware of UK tax year dates and why:

• Employees and individuals working in the United Kingdom 

• Have freelance income or own a company 

• Hold UK property or investments.

• Are you submitting a UK Self-Assessment tax return

• Obtain government support or British pensions

April 6 might appear to be an arbitrary date at first glance; however, this date is actually a remnant of centuries-old traditions and calendar reforms that took place in the country. Originating from the switch from the Julian Calendar to the Gregorian Calendar, this date is not the official tax administration date followed throughout the country. 

So next time you look at your tax return and wonder why it starts on 6 April instead of 1 January, you’ll know it’s not a mistake—it’s history, preserved in numbers.