First off you need to register for Self Assessment by the 5th October before the January 31st Self Assessment submission deadline. 

So that means if you need to complete a Self Assessment for the 2018/19 tax year (6 April 2018 – 5 April 2019), you need to register for Self Assessment by 5th October 2019.

You then need to file this Self Assessment Tax Return by 31 October  2019 or online by 31 January 2020.

To register, you’ll need a Government Gateway account with HMRC which proves your identity when accessing your Self Assessment online. 

There are 2 ways you can submit your Self Assessment tax return and they are: 

  1. Online 
  2. Paper form by post

HMRC and Dead Simple Accounting strongly recommend taxpayers to file online because: 

  • It’s secure and convenient 
  • The tax calculations show automatically for you, in real time
  • There’s help & guidance you can access whilst preparing the return 
  • You can save your work and return later 
  • You’ll get an acknowledgment straight away after submitting that your return has been received by HMRC 
  • And lastly if you are owed a tax refund, the money you will be repaid faster by submitting the return online 

To register just visit www.gov.uk/register-for-Self Assessment 

There are then 2 routes to go down: 

If you are self-employed 

Filed a return before?  If you sent a return before you can register again using form CWF1, but you will need your 10 digit Unique Taxpayer Reference (UTR) from when you registered before (your UTR is on all letters from HMRC)

Not filed a return before? If you haven’t sent a return online before you’ll need to register online on HMRC’s site. 

HMRC will post your 10 digit Unique Taxpayer Reference (UTR) and also an activation code within 2 weeks from you completing the registration. 

Once you’ve got your activation code you’ll need to go back online and activate your account to access your online Self Assessment form. 

If you are NOT self-employed 

The process is similar to the above but as you are not self employed you need to complete form SA1 instead.

Paying your tax 

You have to make a payment for the tax bill by 31st January. 

But it might be possible for HMRC to collect your tax throughout the following year via your PAYE tax code. This is allowed if:

  • You are paid as an employee (via PAYE) e.g part time employed and part time self employed
  • You file your return online by 31st December, or you file your paper return by 31 October 
  • You owe no more than £3,000 in tax
  • You have a PAYE tax code