The UK tax year runs from 6 April to 5 April (a quirk inherited from the old calendar system), so 2026/27 means 6 April 2026 to 5 April 2027. Every annual figure resets on 6 April: Personal Allowance, ISA allowance, CGT exemption, dividend allowance, pension annual allowance.
The rhythm drives every deadline that follows: Self Assessment registration by 5 October, online filing and payment by 31 January, payments on account each 31 January and 31 July, and MTD quarterly updates through the year. The tax deadlines calendar lays them all out with free email reminders.
Selling an asset on 4 April books the gain into the closing tax year; waiting until 6 April books it into the new one, resetting a fresh £3,000 CGT exemption and pushing the payment deadline a full year further out. The same two-day trick applies to bonuses, dividends and pension timing, all because of where 5 April falls.
