Use gross figures before refrigerant, parts, or F-Gas certification costs are deducted.
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.
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.
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.
| 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 |
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.
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.
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.
Yes, F-Gas certification and renewal fees, along with specialist testing and recovery equipment, are standard allowable expenses for this trade.
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.
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.
Our free calculator checks your exact threshold, deadlines, and recommends the easiest software for your record-keeping.
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