MTD for Air Conditioning & Refrigeration Engineers —
Contracts and Your Threshold
Use gross figures before refrigerant, parts, or F-Gas certification costs are deducted.
- The same £50k / £30k / £20k phased MTD thresholds apply as any self-employed sole trader, commercial AC and refrigeration contracts are among the higher-paying trade specialisms.
- Ongoing maintenance contracts are recognised as income as each visit is invoiced, not as one lump sum when the contract is signed.
- F-Gas certification, refrigerant costs, and specialist testing equipment are all standard allowable expenses.
If you're a self-employed air conditioning or refrigeration engineer, working on domestic installs, commercial systems, or ongoing maintenance contracts, Making Tax Digital applies to you the same way it applies to any sole trader. Commercial AC and refrigeration work often pays well, and ongoing maintenance contracts have their own timing quirk worth understanding.
Are You Affected by MTD as an AC or Refrigeration Engineer?
Yes, if your gross trade income, plus any other self-employment income, exceeds the relevant threshold:
| Tax Year Assessed | Threshold | MTD Start Date |
|---|---|---|
| 2024–25 | Over £50,000 | 6 April 2026. Live since April 2026 |
| 2025–26 | Over £30,000 | 6 April 2027 |
| 2026–27 | Over £20,000 | 6 April 2028 |
Your gross income is your total invoiced amount before expenses, refrigerant, parts, and certification costs are all deducted afterwards, not before, when checking your threshold.
Maintenance Contracts — When Does the Income Count?
Many engineers in this trade hold ongoing service and maintenance contracts with commercial clients, covering quarterly or annual servicing of AC and refrigeration units. Under the cash basis, which most self-employed engineers use, this income is recognised as each visit or service period is invoiced, not as a single lump sum at the point the contract is agreed. A 12-month contract worth £6,000, invoiced quarterly, adds £1,500 to your income each quarter it's billed, not £6,000 all at once.
What You Can Claim
| Expense Category | Examples |
|---|---|
| Certification | F-Gas certification and renewal costs |
| Refrigerant and parts | Refrigerant gas, compressors, and system components |
| Testing equipment | Gauges, leak detectors, recovery machines, via capital allowances |
| Vehicle costs | Van running costs or mileage, at the current HMRC rate |
| Insurance | Public liability and professional indemnity cover |
F-Gas Costs, Refrigerant and Contract Records
Refrigeration and air-conditioning work carries regulated costs that other trades do not have, from F-Gas certification to refrigerant stock and recovery. Recording them separately keeps the margin on each job visible.
- Keep F-Gas certification and renewal costs, and any company or personal registration fees.
- Record refrigerant purchases against the jobs where it was used, and keep recovery and disposal receipts.
- Log planned-maintenance contracts with the invoice schedule, and record each payment when it is received.
- Keep calibration and replacement costs for gauges, leak detectors and recovery units, treating larger items as capital.
- Keep commissioning and compliance records, which support both the invoice and your obligations.
Common MTD Mistakes for AC and Refrigeration Engineers
- Recording only invoices paid by card. Trade accounts and commercial contracts often pay by bank transfer weeks later.
- Treating gas cost as reducing income. The threshold is tested on the amount you invoice, before gas and parts.
- Skipping annual contracts. A maintenance contract paid up front belongs in the quarter you receive it.
- Mixing subcontracted installs with your own work. If you pass on work, record your fee and any recharge consistently.
- Forgetting van stock. Parts and gas carried in the van still need receipts.
A Sample Quarter: What the Update Looks Like
A sample quarter for an engineer with a mix of contract, install and repair income in the summer peak.
| Q2: 6 July to 5 October 2026 | Amount |
|---|---|
| Maintenance contracts | £9,800 |
| Installs and commissioning | £12,600 |
| Call-outs and repairs | £5,300 |
| Total income | £27,700 |
| Refrigerant and parts | £7,400 |
| Van, fuel and insurance | £2,900 |
| F-Gas, tools and calibration | £1,350 |
| Subcontract labour | £2,200 |
| Total expenses | £13,850 |
| Profit for the quarter | £13,850 |
Summer typically boosts call-outs and installs. The next quarter will look quieter, but the update is still required.
Worked Example
Adnan — Self-employed AC and refrigeration engineer
Adnan's £60,500 combined income exceeds the £50,000 Phase 1 threshold. His maintenance contract income is counted as each quarterly visit is invoiced across the year, not as one lump sum.
Frequently Asked Questions
When does income from a maintenance contract count towards my threshold?
As each visit or billing period is invoiced, not as one lump sum when the contract is signed. A 12-month contract billed quarterly adds to your income each quarter it's invoiced, spread across the tax year.
What's the MTD threshold for AC and refrigeration engineers?
The same as any self-employed sole trader: over £50,000 gross income in 2024–25 means MTD from April 2026, over £30,000 in 2025–26 means April 2027, over £20,000 in 2026–27 means April 2028.
Can I claim my F-Gas certification costs?
Yes, F-Gas certification and renewal fees, along with specialist testing and recovery equipment, are standard allowable expenses for this trade.
Does commercial contract work count differently from one-off domestic jobs?
No, both are simply combined into one gross trading income total for your MTD threshold check, there's no separate treatment for contract versus one-off work.
What software do I need as a self-employed AC engineer?
Any HMRC-recognised MTD software works. The main practical need is tracking recurring contract billings alongside one-off job invoices, which most trade invoicing software handles well.
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