Should I submit my return early ?

The tax year has ended.

Main benefit of submitting tax return as soon as possible is that the enquiry window runs for a full 12 months from the date the tax return is received. So for example a return received by HMRC on 20 June 2018, the enquiry window will run to 20 June 2019 – EM1501

I have already filed mine.

Fascinating facts about Self Assessment