SA102 Form: A Simple Guide for Employees Filing Self Assessment

For many employees, PAYE feels like the end of the tax story: money in, tax out, nothing more to see here. But if your year included a second job, a shiny new directorship, or perks like a company car, HMRC may want you to add a little extra detail to your Self Assessment. That’s where the SA102 form makes its entrance.

Think of it as the supporting actor to your main tax return—the page that catches all the “oh, and another thing” details from your working life. Without it, your return can look a bit unfinished (and nobody wants HMRC sending follow-up questions). With it, everything slots neatly into place, giving you a cleaner, more accurate picture of your income for the year.

What is the SA102 form?

The SA102 form is a supplementary page of your Self Assessment that focuses on employment. It’s where you record:

• Your salary and wages
• Any tax reliefs you’re claiming
• Employment expenses (e.g. travel or professional fees)
• Employer-provided benefits (such as a company car or healthcare)

Think of the SA100 as your main tax return form. It gives HMRC the overview. The SA102, on the other hand, is the zoom-in on your employment income. If the SA100 is the “headline,” the SA102 is the detail that makes sure your story is complete.

You’ll find the form and HMRC’s official helpsheets on GOV.UK. To fill it in, you’ll need your National Insurance number and paperwork from your employer—such as a P60 or P11D.

📌 Pro Tip: If you’re a company director, you’ll almost always need to file a Self Assessment tax return—even if most of your income was already taxed through PAYE—so check whether the SA102 applies to you.

Who needs to complete an SA102?

Not every employee will need the SA102. If your PAYE deductions cover everything and there’s nothing unusual about your income, you may not have to file it at all. But you will need the SA102 if you fall into one of these groups:

• Employees who need to declare income or benefits that aren’t fully handled through PAYE.
• Directors (especially of a close company) who must report salary, benefits, or perks.
• Anyone with a PAYE tax reference who has additional employment details to declare.
• Employees with foreign income linked to their job.

Examples of when the SA102 applies:

• Claiming employment expenses such as mileage allowance, business travel, subsistence, credit cards, professional fees, or subscriptions.
• Reporting employer-provided benefits, such as low-interest loans, company cars, or healthcare.
• Declaring employment tax adjustments, including capital allowances or balancing charges.

In short, if your working life involves more than just a single payslip, the SA102 helps ensure your UK tax return is accurate and complete.

📌 Pro Tip: Even small items like reimbursed expenses or professional subscriptions can trigger the need for an SA102. If you’re unsure, check your P11D or HMRC guidance—leaving things out often causes more hassle than including them.

What income and details go on the SA102?

The SA102 doesn’t just ask for your job title and salary—it drills down into the finer details of your employment for the year. From your employer’s PAYE reference to the value of that private healthcare plan, this is where you record everything HMRC needs to see about your work income and related benefits.

Here’s what typically goes on the form:

• Employment income: Salary, wages, bonuses, tips
• Employer details: Name, address, PAYE tax reference
• Benefits in kind: Private medical or dental insurance, company car, low-interest loans
• Expenses and payments: Business travel, mileage allowance, subsistence, credit cards, reimbursed costs
• Tax reliefs: Allowable professional fees and subscriptions
• Adjustments: Employment-related capital allowances and balancing charges

To get these figures right, you’ll usually lean on your employer paperwork: your P60 for year-end pay and tax, a P45 if you left mid-year, and a P11D for benefits. Payslips are also useful as a cross-check.

Some roles come with extra requirements:

• Company directors must include directorship income, even if PAYE has already covered most of it.
• Foreign income tied to employment must be declared, even if taxed abroad.
• Welsh taxpayers may need to apply Welsh income tax rates.

📌 Pro Tip: Treat your P60, P45, and P11D as a checklist. If it appears on one of these forms, it almost certainly needs a home on your SA102.

How to fill out the SA102 form

The SA102 is designed to capture the full picture of your employment income and benefits. It may look formal, but if you take it step by step, it’s surprisingly straightforward.

1. Gather your paperwork: Collect your employer’s name and PAYE tax reference, your Unique Taxpayer Reference (UTR), your National Insurance number, and the figures from your P60 or P45. If you received benefits such as medical insurance or a company car, you’ll also need your P11D.
2. Enter your income: Fill in the sections for salary, wages, tips, and bonuses. Use your P60 (or P45 if you left a job) to make sure the numbers are accurate.
3. Add expenses and reliefs: Record allowable employment expenses—such as mileage allowance, business travel, subsistence costs, and professional fees or subscriptions—along with any tax relief you are claiming.
4. Include benefits in kind: Add details of employer-provided benefits, from low-interest loans to private medical or dental insurance, as well as reimbursements made through credit cards or expense payments.
5. Check for adjustments: If you’ve claimed employment-related capital allowances in the past, include any necessary balancing charges.
6. Submit with your SA100: Attach the SA102 supplementary pages to your main SA100 tax return (on paper or online). Review GOV.UK helpsheets to confirm you’ve completed every section correctly.

If anything looks unclear—especially around capital allowances, foreign income, or Welsh rates of income tax—HMRC’s guidance and helplines are there to help.

📌 Pro Tip: Double-check that the figures you enter are the gross amounts (before tax) shown on your P60 or P45. It’s a common mistake to use take-home pay, and it can throw your Self Assessment off balance.

SA102 vs. self employment: What if I’m also self-employed?

It’s increasingly common to wear two hats: employee during the day, freelancer or business owner after hours. If that’s you, HMRC wants to see both sides of the picture.

The SA102 covers your employment income—salary, benefits, and expenses from an employer. The SA103 is the supplementary page for self-employment, where you declare income from your own business, side hustle, or freelance work.

You’ll need to complete both forms if you:

• Have a part-time business alongside employment.
• Receive a salary as a company director but also trade in your own name.
• Work in a close company where you’re both an employee and shareholder.
• Live in Wales, where different income tax rates may apply on your combined income.

HMRC uses the SA102 and SA103 together to calculate your total taxable income, any tax reliefs, and whether capital allowances or balancing charges apply. The key is to treat them as complementary, not either/or—they build a full picture of your working life for the tax year.

📌 Pro Tip: Don’t assume expenses can be claimed in both places. Travel costs for your employment go on the SA102; costs linked to running your own business belong on the SA103. Keeping them separate avoids confusion and protects your tax relief.

Common mistakes and how to avoid them

Even with the best intentions, it’s easy to trip up on the SA102. Most errors come from either leaving things out or putting them in the wrong place. The good news? A quick check against your paperwork usually solves the problem before it reaches HMRC’s desk.

Some of the most common pitfalls include:

• Mixing up employment and self-employment details.
• Forgetting to add professional fees or subscriptions.
• Missing balancing charges from previous capital allowance claims.
• Overlooking employer-provided benefits like credit cards or subsistence expenses.
• Failing to claim tax relief for eligible mileage allowance or other employment expenses.

To avoid these mistakes, make sure you double-check your payslips, P60, P45, P11D, UTR, and employment details before you file. Lining everything up in advance not only makes the form quicker to complete but also reduces the risk of costly amendments later.

📌 Pro Tip: Always review your SA102 line by line against your P60 or P11D before pressing “submit.” It takes minutes, but it’s the simplest way to catch missing benefits or mis-entered figures that could otherwise slow down your Self Assessment.

When and how to file the SA102 with your Self Assessment

The SA102 isn’t filed on its own—it travels with your main Self Assessment tax return, the SA100. Together, they form the complete picture of your income for the tax year.

Deadlines to remember:

• Paper returns: 31 October following the end of the tax year
• Online returns: 31 January following the end of the tax year

These deadlines apply to both the SA100 and the SA102. Missing them can lead to late filing penalties, so it pays to get your paperwork ready early.

If you realise after filing that you’ve left something out—such as a change in directorship, a capital allowance adjustment, or a forgotten balancing charge—you can usually amend your return within 12 months of the filing deadline. This can be done online through your HMRC account or by sending a paper amendment.

To check your return status, log in to your HMRC online account, where you’ll see confirmation that your Self Assessment (including the SA102) has been received and processed. If HMRC raises a query about your employment details, respond promptly and keep your supporting documents—like P60s, P45s, and P11Ds—close to hand.

📌 Pro Tip: Don’t wait until January to file. Submitting your SA102 and SA100 early not only avoids the deadline rush but also gives you more time to correct errors or claim reliefs if you’ve overlooked something.

Keep your SA102 simple

The SA102 isn’t a headache—it’s just the form that keeps your employment details tidy and your Self Assessment on track. Get your paperwork together now, and January becomes smug, not stressful.

Not sure if you’ve covered everything? Book a free financial review with a tax adviser through Unbiased. You’ll get clear answers, tailored advice—and one less thing to worry about at tax time.

Frequently Asked Questions (FAQ)