Self Assessment Tax Return Checklist and Tips

Anyone who is used to completing tax returns will tell you that there is a great deal of information required in order for you to complete one on time without becoming very stressed! If only there…

5 Minute Read

Last Updated: 26th September 2023

Anyone who is used to completing tax returns will tell you that there is a great deal of information required in order for you to complete one on time without becoming very stressed! If only there was an easy to follow, comprehensive tax return checklist available…

Many people find themselves rushing to input all relevant information before the deadline, which often causes mistakes – resulting in costly penalties.

To make things easier, taxation specialists GoSimpleTax have gone ahead and put together this quick and easy self-assessment checklist to have by your side throughout the process. Including deadlines for completing your self-assessment and the personal tax return items you’ll need.

Avoid the dreaded rush of a last-minute tax return and read on to discover everything you’ll need to complete your tax return.

Before You Begin

Do You Need to Register Self Assessment?

It isn’t just sole traders who need to fill in a tax return. Find out if you need to do so here.

If you haven’t registered for self-assessment, you should do so here immediately. You should allow seven to ten days for your UTR to arrive.

You will also receive a PIN number that allows you to register for the Government Gateway, giving you access to the HMRC online services.

? My PIN has arrived

? I have my UTR number

? I have a Gateway ID 

Partners and members of LLPs should register here, and in non-LLP partnerships, one member should also be nominated to register the partnership itself.

? I have registered 

Self Assessment Tax Returns Deadlines

Your tax return covers the financial year from 6th April of the year before to 5th April of the year the self-assessment refers to.

You should complete your tax return online by 31st January each year, or by post by the 31st October each year.

? I have found the correct deadline for my purposes 

Find the right self-assessment form

The basic self-assessment form is called the SA100. The paper version, plus a useful guidance sheet, can be found here.

? I have downloaded the SA100 ready for completion 

Supplementary Forms

Depending on your circumstances, you may also need to fill in the following:

If you have additional wages or other income from employment you’ll need an SA102.

? I have downloaded my SA102 ready for completion 

If you’re self-employed, and your annual turnover is below £85,000 (the current VAT cut-off point), you should complete an SA103S.

? I have downloaded my SA103S ready for completion 

If you’re self-employed and your turnover is above £85,000, you need to fill in an SA103F.

? I have downloaded my SA103F ready for completion 

If you belong to a partnership, each partner should fill in either a short (SA104S) or full (SA104F) partnership form, depending on the nature of their income and activities.

? I have downloaded my relevant partnership form (SA104S or SA104F) ready for completion 

If you’re in a non-LLP partnership, one member will also have to complete an SA800 for the partnership itself.

? I know who is completing the SA800 

If you’re a landlord, or otherwise receive income from property, you’ll need an SA105.

? I have downloaded my SA105 ready for completion 

If you receive income from work, investments or other sources not based in the UK, you need to complete an SA106.

? I have downloaded my SA106 ready for completion 

If you receive income from a trust or settlement, you’ll require an SA107.

? I have downloaded my SA107 ready for completion 

If you have made money through capital gains, you should complete an SA108.

? I have downloaded my SA108 ready for completion 

If you do not reside in the UK but are still required to pay tax to the UK government, you’ll need an SA109.

? I have downloaded my SA109 ready for completion 

? I have downloaded all relevant supplementary forms 

Documents and Information Checklist

To fill in your tax return, you will need information regarding the following:

? National Insurance Number

? Unique Taxpayer Reference number (see above)

? Activation PIN (see above)

? Company/partnership name, address and company number if relevant

? Your business’s annual income and expenditure.

? Income earned from other employment

? Any rent you have received
? Interest paid on loans, credit cards or other credit

? Any savings

? Income from overseas

? Income received from a partnership

? Any dividends received

? Benefits received either from the state or an employer

? Capital gains received

? Gift Aid received

? Pension contributions

? Tax payments you’ve already made this year (payments on account)

(Check each once you have located it)

You may also need:

? Your P45

? Your P60

? Certificates detailing interest you’ve received from your bank

? All expenses receipts

? Your P11D

? Your P2 coding notice 

Expenses Claims

You may be able to claim back certain business expenses, including expenditure on:

? Travel
? Staff
? Premises
? Legal and Financial Services
? Clothing
? Marketing, Subscriptions and Entertainment

(Check the areas you know you are eligible to claim for.)

Find full details of what you can claim here.

Time to Begin

Once you have everything ready, it’s time to:

? Complete all relevant forms carefully 

(You can save your online self assessment and return to it at a later date if necessary, so don’t rush!)

? Submit all forms after checking 

(You can edit everything right up until you reach the submission page.)

? Pay your tax before the deadline 

(You can work out a payment plan if necessary.)


To make matters easier, you can use the GoSimpleTax app or online tools to upload your receipts in real time and quickly and easily submit all information to HMRC. The software will automatically check for possible mistakes and notify you if there are any expenses claims you can make.

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Blog content is for information purposes and over time may become outdated, although we do strive to keep it current. It's written to help you understand your Tax's and is not to be relied upon as professional accounting, tax and legal advice due to differences in everyone's circumstances. For additional help please contact our support team or HMRC.

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