Guide to Self Assessment Forms​

What's it all about?

This article's designed to help:

• Understand what the Self-Assessment system is and who needs to use it
• Get to grips with the basic Self-Assessment tax return forms and which you need to use for you situation
• Keep yourself safe from HMRC's Self-Assessment fines and penalties

When is the Self Assessment tax return deadline?

Dive into the streets with us as we hit the pavement to find out if people know when the self-assessment tax return deadline is!

Most people in the UK never have to think about how their tax gets calculated or collected. Everything’s handled for them automatically through the Pay As You Earn (PAYE) system, with the Income Tax and National Insurance Contributions (NICs) they owe already taken out of their pay by their employers before they get it. 

But there are millions of people across the country who have all sorts of income that can’t be taxed that way because those earnings don’t come through an employer who can calculate that tax and pay it to HMRC. 

That’s where the Self Assessment tax return system comes in.

What kinds of income do you have to report via Self-Assessment?

It’s not just the self-employed who have to use Self Assessment tax returns to tell HMRC about their money situation. For example, you might still also need to use Self Assessment if you:

• Are a partner in a business partnership.
• Earn money that isn’t taxed through PAYE—like rent, for instance.
• Get a commission from your job—or even tips!
• Get income from savings, investments or dividends.
• Have money coming in from abroad.
• Are claiming a tax refund and have over £2,500 of expenses to claim for.
• Are a company director, religious minister or the executor of an estate.
• Are getting Child Benefit and have an income of over £50,000.
• Have Capital Gains to report. You can read more about these here.
• Are paid in cryptocurrencies or make profits from selling or exchanging them.

We know—that’s quite a list, right? That’s one of the reasons why so many people get tangled up in the regulations.

Leaving the taxman waiting when he’s expecting a tax return from you can get messy—and expensive—very fast. We’ll talk more about that in a bit, but for now just remember that you really can’t afford to ignore a demand for Self Assessment paperwork from HMRC, even if you’re positive it’s just a mistake.

How do you complete Self-Assessment?

With Self Assessment, you use a tax return form to report all your untaxed income to HMRC. You also report information such as the costs of running your business or maintenance expenses for a property you rent out so that these “allowable expenses”. can be deducted from your tax bill. 

For example, when you’re self-employed, it’s not your overall income you’re being taxed on. Instead, the taxman’s only after a bite of your actual profits after your essential costs have been paid. So far so good—but here’s where it starts to get trickier.

There are lots of fiddly little rules about what actually counts as an “allowable expense” in difference circumstances, of course, and that’s an important thing to keep in mind. It’s easy to get tripped up if you don’t understand the system and errors in your tax return can result in a penalty notice from HRMC.

Depending on the type of income you need to report to HMRC there are a number of different forms you will need to complete – either online or in hardcopy.

Self-Assessment Forms

Let's see what the paperwork looks like...

Form SA100—the main Self Assessment tax return

This is the big one. You can fill it in and submit it entirely online, or download it and print it out to send later by post. If you do it online, then HMRC will a few simple questions at the start to narrow down which sections of the form apply to you. That’ll save you from wading through a pile of unnecessary pages.

Form SA100 will tackle all the big questions HMRC has about you and your money. It’s where you’ll report your untaxed income, any business expenses that count against your profits and a lot of other important stuff. If you’re self-employed in construction, for instance, it’s where you’ll claim back any tax you’re owed through the Construction Industry Scheme (CIS).

Form SA102—employees or company directors

This is the first of several add-on “supplementary pages” that you might need to use when you’re filing your Self Assessment tax returns. Form SA102 comes in when you’re the director of a company or have employment income to report alongside your self-employment earnings.

Form SA103S or SA103F—self-employment

SA103S is a supplementary form for reporting self-employment income when your “turnover” (total business income) in a tax year is under the VAT threshold. The “S” in the name means it’s the short version of the form. If your turnover goes over the VAT threshold, you’ll be using the “full” version of the form instead, which is called SA103F.

Form SA104S or SA104F—business partnerships

When you’ve got income from a business partnership to report, you’ll use one of these forms to do it. As with the self-employment pages, there are short and long versions of these forms. The one you use depends on your situation. If you’re only reporting trading income from a partnership and interest or “alternative finance” receipts (from crowdfunding, etc.), for instance, you can use the short version.

Form SA105—UK property income

Whether you’re renting out a room in your own home or letting out entire UK properties, you’ll need to tell the taxman about the money you’re making and the expenses you’re coughing up. Either way, form SA105 will need to be added to your tax return to do this. The exception is if the income comes from land or property overseas, although you can still use SA105 to report furnished holiday accommodation earnings in the European Economic Area.

Form SA106—foreign income or gains

When you’ve got money coming in from overseas, you may still have to pay UK tax on it. Depending on your situation, that could mean foreign wages, investments, rental income or pensions. A lot depends on whether you’re a “UK resident” for tax purposes, so get advice if you’re not 100% sure where you stand. If you do have to pay tax on your foreign earnings, you’ll need to include form SA106 in your Self Assessment paperwork.

Form SA108—Capital Gains

Capital Gains are the profit you get when you “dispose of” (sell, swap, claim compensation for or even just give away) something that’s gone up in value since you bought it. As you’ve probably guessed, there’s a maze of rules, exemptions and thresholds to pick your way through here, and it’s very easy to get tripped up if you don’t know the territory. Depending on your circumstances, the “assets” you pay Capital Gains Tax on could include jewellery, works of art or personal possessions worth over £6,000. Whatever it is, you can report the gains (or losses) you’ve made in form SA108.

You can report your capital gains in a Self Assessment tax return in the tax year after you sold or disposed of an asset

Not sure if you need to declare it to HMRC? Check out our beginners guides to capital gains tax.

Form SA109—non-UK residents or dual residents

Residence status is a huge part of UK tax law. Your status affects the kinds of tax you pay, along with which sources of income you pay it on. That means it’s incredibly important to get your residence paperwork right. Form SA109 will help you explain your residence and domicile (where your permanent home is) to the taxman.

...and the rest

The exact Self Assessment forms you need to file will vary with your personal and financial situation. We’ve already covered most of the major ones, but here are a few more examples that might apply to you:

• SA102M: ministers of religion.
• SA102MP: Parliament.
• SA102MLA: Northern Ireland Legislative Assembly.
• SA102MSP: Scottish parliament.
• SA102WAM: The National Assembly for Wales.
• SA103L: Lloyd’s underwriters.
• SA107: Trusts, etc.
• SA110: tax calculation summary.

Getting it wrong: Self-Assessment penalties

The Self Assessment system comes with a range of fines and penalties that start to kick in the moment you miss a deadline or don’t stick to the rules. For example, if you miss the main deadline of the 31st of January for filing your tax return and paying up what you owe, you’ll be hit with an automatic £100 fine. If you keep HMRC waiting after that, things just keep getting worse:

• Missing the filing/payment deadline on the 31st of January: £100.
• Leaving it for another 3 months: £10 per day, up to £900.
• Still haven't done it after 6 months: £300 or 5% of what you owe (whichever's worse).
• A year past the deadline without sorting it out: another £300 or 5% of the tax owed.

Even if you get your Self Assessment paperwork in on time, things can still get bad if your numbers don’t add up. Making a mistake in a tax return can be painful when the taxman catches on. Deliberately lying in a Self Assessment form is even worse. If you’ve just made an honest mistake, there’s a chance you’ll be able to fix the problem before the penalties start rolling in. You have to do it within 12 months of the deadline, though. If you do your taxes online, this can be as simple as logging in and correcting the error. If you file on paper, though, it can get a little more complicated. You've got to download another copy of the Self Assessment form and send in the pages you've changed. The main thing is to be honest and up-front as soon as you realise there’s a problem in your paperwork. If the taxman thinks you’ve deliberately understated your income, over-claimed for business expenses or even just been careless with your bookkeeping, things can get bad very quickly.

That said, HMRC does understand that life can sometimes get in the way of your Self Assessment homework. If you’ve got a reasonable excuse for missing a deadline or giving incorrect information, for instance, you might be able to limit or avoid the damage. What’s a reasonable excuse in the taxman’s eyes? Well, it’s a short list, but here are a few examples:

• HMRC itself made a mistake and either gave you bad advice or never even told you that you were supposed to file Self Assessment tax returns.
• You were hit by serious illness or other critical personal circumstances.
• A technical error you had no control over or knowledge about messed up your filing.
• Your tax return got tangled up in postal delays or bank errors.

Keep checking back here for more money tips and updates. We’re experts at saving you cash and we’re always here to help. That’s the reason why you’re better off with RIFT.

RIFT Roundup: what it all means

• Self Assessment: A way of declaring untaxed income and other financial information to HMRC.
• Supplementary forms: Add-ons to your tax return to report specific circumstances affecting your tax.
• Capital Gains Tax: a capital gains tax is a tax you pay when you “dispose of” certain kinds of asset at a profit.