ADI HMRC Self-Assessment Guide: Expenses, SA103S & Tax Tips

Introduction

Most ADIs are self-employed sole traders. That means a Self Assessment tax return every year, a 31 January deadline, and the creeping dread that starts around November when you realise you haven't kept proper records.

At £36–£40 per lesson — the most common price bracket according to the DVSA's 2025 survey — a full-time ADI doing 25 hours a week is turning over somewhere between £46,000 and £52,000 a year. That's a serious income. HMRC will want their share. But only their fair share.

The difference between paying too much and paying the right amount comes down to one thing: knowing what you can claim. This guide walks you through the whole picture — from whether you need to file at all, to the exact expense categories on the SA103S, to the habit that makes January genuinely stress-free.

Do You Need to File a Self Assessment?

If you're self-employed as an ADI and earning above the £1,000 trading allowance, yes — you need to file. There's no getting around it.

Most ADIs will use the SA103S — the short-form supplementary self-employment pages that attach to your SA100 main return. You qualify for the short form as long as your annual turnover is below the VAT registration threshold, which sits at £90,000 for 2025/26. The vast majority of driving instructors fall comfortably under that.

The key boxes on the SA103S are straightforward once you know what they're asking:

Box 9 — your total receipts (gross turnover from lessons and any other self-employment income)
Boxes 17–20 — your allowable expenses, broken down by category
Box 28 — your net profit (turnover minus allowable expenses)

That net profit figure in Box 28 is what you pay tax on. So every legitimate expense you claim reduces it — and reduces your bill.

What Counts as Turnover (Box 9)

Box 9 is your gross income — everything that came in before you deduct a single penny. For most ADIs that means:

All lesson income, whether paid per lesson or in block bookings
Any income from PDI training or mentoring if you offer it
Franchise fees received, if you sub-franchise to other instructors

Don't net anything off here. Gross in, gross out. The deductions come in Boxes 17–20.

Allowable Expenses: What You Can Claim

This is where most ADIs leave money on the table. Not through dishonesty — through not knowing what's claimable. Here's a category-by-category breakdown.

Motor Expenses

Fuel is almost certainly your biggest single cost. You have two options: claim actual fuel costs (with receipts), or use HMRC's approved mileage rate — 45p per mile for the first 10,000 business miles in a tax year, dropping to 25p per mile after that. The mileage rate is simpler and often more generous for high-mileage instructors.

Beyond fuel, you can also claim:

Car insurance for your dual-control teaching vehicle
MOT and servicing costs
Tyres and other consumables
Breakdown cover
The cost of dual controls themselves

One important caveat: if you use the same car for personal journeys, you can only claim the business proportion. So if 80% of your mileage is teaching, you claim 80% of those costs. Keep a mileage log — it's the only way to defend that split if HMRC ever asks.

Phone and Stationery (Box 18)

Your mobile phone bill is claimable — the business proportion of it. If you use your phone for both personal and business purposes, you'll need to make a reasonable estimate of the split. Most ADIs use their phone heavily for booking management, pupil communication, and navigation, so a 70–80% business use figure is often defensible.

Also claimable here: stationery, printing costs, and any postage related to the business.

Advertising (Box 19)

Anything you spend to bring in pupils is claimable:

Website hosting and domain costs
Google Ads and Facebook advertising
Business cards and flyers
Local directory listings

Note that client entertainment — taking a pupil out for a coffee, for instance — is generally not allowable. HMRC is quite firm on this.

Professional Fees (Box 19)

This category covers the costs of running a legitimate, compliant business:

Accountant or bookkeeper fees
ADI registration renewal fees paid to DVSA
Professional association memberships — DIA, ADINJC, and similar
Public liability insurance
Software subscriptions used for the business — lesson management tools, accounting software, and so on

Other Allowable Expenses (Box 20)

A few things that don't fit neatly elsewhere but are still claimable:

CPD courses and training directly related to your work as an ADI
Hazard perception or theory test materials you supply to pupils
Branded clothing or uniform that carries your business name — a polo shirt with your school's logo, for example

What You Cannot Claim

Just as important as knowing what's in is knowing what's out:

Personal clothing — even if you wear it every day for work, plain clothes don't qualify
Fines — parking tickets, speeding fines, and the like are never allowable
Personal phone calls — only the business proportion of your bill is claimable

The question of commuting from home to your first lesson is a genuine grey area. Because your home is effectively your base of operations as a sole trader, HMRC may treat that first journey as a business journey — but it's worth getting specific advice from an accountant rather than assuming either way.

The Tax Year: 6 April to 5 April

The UK tax year does not follow the calendar year. It runs from 6 April to 5 April the following year. So the 2025/26 tax year runs from 6 April 2025 to 5 April 2026.

Your Self Assessment return for that period is due by 31 January 2027 if you file online. Miss that deadline and you're looking at an automatic £100 penalty — even if you don't owe any tax.

One thing worth knowing: you don't have to wait until January. You can file as soon as the tax year ends on 5 April. Filing early means you know exactly what you owe — and if you're due a refund, you get it sooner. There's no benefit to leaving it late.

The Real Problem: Most ADIs Don't Keep Records Throughout the Year

Let's be honest about why January is stressful. It's not the tax return itself — the SA103S is a fairly short document. The stress comes from trying to reconstruct six months of financial activity from memory.

You're hunting through bank statements for fuel receipts. You've forgotten about the CPD course you paid for in September. You can't remember whether that car service was in this tax year or the last one. You find a receipt for something and genuinely can't recall what it was for.

The solution isn't a better accountant. A good accountant can only work with what you give them. The solution is better habits throughout the year — specifically, logging income and expenses at the time they happen, not three months later.

How to Make This Painless: Log As You Go

The principle is simple: every lesson is income. Every fuel stop is an expense. Log both at the time, not three months later.

Categorise expenses as you go — motor, phone, advertising, professional fees, other. Use the same categories HMRC uses on the SA103S, so there's no translation work at the end of the year.

By the time April comes around, your numbers are already there. You're not reconstructing anything — you're just exporting. Hand the figures to your accountant, or enter them directly into your return. Either way, it takes an hour rather than a weekend.

The ADIs who find tax season genuinely painless aren't doing anything clever. They're just logging as they go. That's the whole secret.

How LessonOps Helps

LessonOps tracks your income lesson by lesson and lets you log expenses in the categories HMRC actually uses — motor, phone, advertising, professional fees, and other allowable expenses. At the end of the tax year, you export a clean CSV and hand it to your accountant.

No shoebox. No panic. No guessing.

It's built around the UK tax year — 6 April to 5 April, in GBP — the way it should be for a UK driving instructor. Free to start at lessonops.com.