Is it better to file your Self Assessment tax return as soon as possible after the end of the tax year?
You are not obliged to file your tax return for 2015-16, online, before the 31 January 2017. However, if you leave the process of completing your return until close to this date, it will not give you much time to calculate and fund the amount of tax you may owe on the same date, 31 January 2017.