Friday is the deadline for filing your 2001/02 tax return here in the UK and as usual I’ve left it to the last minute. Well, almost the last minute. I filed my return today using the Inland Revenue’s on-line filing service for the first time.

The system worked well for me, despite receiving some bad press earlier in the year regarding its security. I was able to complete the tax return form quite easily and more quickly than in previous years because the system only asked me questions that are relevant to my tax situation. I didn’t have to read the entire form in order to work out which bits apply to me. Also, it calculated my tax bill immediately, which inspired a degree of confidence that didn’t exist in the past. Previously it was difficult to know if you had completed the return correctly simply because there was no way of checking it without consulting a tax professional. Now, it’s checked and the numbers crunched in a matter of seconds, and when it turns out as you expected, it’s all very reassuring.

Although the deadline for filing is January 31st, the tax year always ends on April 5th in the UK, and a few weeks ago I wondered how this odd year-end came to be. Thanks to the Internet, I found out. The Notes & Queries section of the Guardian once asked the same question, and Luke of Birmingham had an interesting reply:

The calendar year used to start in March. Hence “September” (7th), “October”, “November” (9th) and “December” (10th). Perhaps the first month of the year was set aside for producing accounts, end of year reconciliations, business plans, mission statements and blue-skies thinking – all important elements of a successful Roman business. Quis enumerabit ipsos fabarum enumeratores?

However, the definitive answer must be that of the Inland Revenue itself, which much to my surprise includes the question on its FAQ:

7. Why does the tax year start on April 6?

The reason for the tax year running from 6 April to 5 April is primarily historical and has its origin in the switch from the Julian to the Gregorian calendar in 1752.
It had been calculated in the 16th Century that the Julian calendar had lost 9 days since its introduction in 46 BC. Most of Europe changed to the new, more accurate, Gregorian calendar in 1582, but this country continued with the old one until September 1752 by which time the error had increased to 11 days.
These 11 days were ‘caught up’ by being removed from the calendar altogether – 2 September was followed by 14 September. In order not to lose 11 days’ tax revenue in that tax year, though, the authorities decided to tack the missing days on at the end, which meant moving the beginning of the tax year from the 25 March, Lady Day, (which since the Middle Ages has been regarded as the beginning of the legal year) to 6 April.
The dates were adopted for income tax on its re-imposition in 1842 and have not changed since.