Conservatory Installer
Tax & MTD Guide

A conservatory installer's tax position is shaped by one thing more than any other: the Construction Industry Scheme. Whether you are fitting a uPVC lean-to onto the back of a terrace, building an orangery base, glazing a roof or finishing the trims and seals, you are doing construction work. That means most of your labour income arrives with 20% already chopped off and paid to HMRC on your behalf, long before you have claimed a single tool or a litre of diesel.

That mechanic, deduct first and reconcile later, is why so many fitters dread the paperwork yet end up with money coming back. This guide walks through how your profit is actually taxed, the specific expenses that belong to this trade, the record-keeping that turns CIS pain into a refund, and the VAT and MTD timing that catches glazing installers out because they supply materials as well as labour.

How Tax Works for a Self-Employed Conservatory Installer

As a sole trader you pay Income Tax on profit: your total income (labour plus any materials you bill) minus allowable expenses. For 2025/26 the personal allowance covers the first GBP 12,570, then you pay 20% to GBP 50,270, 40% to GBP 125,140 and 45% above, with the personal allowance tapering away between GBP 100,000 and GBP 125,140 to create an effective 60% band. Class 4 National Insurance is 6% on profit between GBP 12,570 and GBP 50,270 and 2% above, with Class 2 NIC settled through Self Assessment.

The twist for construction trades is CIS. Your real tax bill is worked out on profit, but the deductions taken from your labour are based on gross labour with no allowance for any of it. Scottish installers pay Scottish Income Tax through six bands (19%, 20%, 21%, 42%, 45% and a 48% top rate) and carry an S-prefixed tax code; Welsh installers have a C-coded tax code at rates currently matching the rest of the UK, with National Insurance staying UK-wide. If a part-time PAYE job or an old code is distorting things, run it through the tax code checker.

CIS: The Deduction That Becomes a Refund

If you fit conservatories as a subcontractor for a builder, a window company or a main contractor, that contractor must verify you with HMRC and deduct CIS from the labour element of your invoices. Register as a subcontractor and the rate is 20%; stay unregistered and it jumps to 30%, so registering is the first job for any new fitter.

Here is why the refund happens. CIS takes 20% off your labour before you deduct your van, tools, fuel, insurance or your GBP 12,570 personal allowance. A fitter invoicing GBP 45,000 of labour has GBP 9,000 deducted across the year, but after expenses and the personal allowance their actual Income Tax and Class 4 NIC are usually well under that. Self Assessment sets the CIS already paid against the real liability and refunds the difference. Our deeper CIS subcontractor guide explains verification, deduction statements and gross-payment status, and you can model your own position with the CIS tax calculator.

The non-negotiable habit: keep every monthly CIS deduction statement from every contractor. No statements, no proof of the tax already paid, no refund.

Allowable Expenses for Conservatory Installers

An expense is allowable when incurred wholly and exclusively for the business. For a fitter the list is dominated by the vehicle, tools and on-site consumables rather than an office.

The Van and Mileage Choice

The vehicle is usually a fitter's single largest cost. You can either claim the business proportion of actual running costs (fuel, insurance, tax, servicing, repairs, plus capital allowances on the van itself) or use HMRC's simplified mileage rate of 45p per mile for the first 10,000 business miles and 25p thereafter. You cannot mix the two for the same vehicle in the same year, so once you start with one method you stay with it for that van. A fitter clocking heavy miles between sites and a builders' merchant, in a thirsty older van, often does better on actual costs; a low-mileage installer with a cheap-to-run van may do better on flat mileage. Work it out once and keep a mileage log either way. Travel from home to a temporary site is generally allowable; ordinary commuting to a fixed base is not.

What You Cannot Claim

The private share of van use, phone and tools must be stripped out. Everyday clothing is never allowable even if you only wear it on site; only genuine PPE and branded workwear count. Parking fines and speeding penalties are never deductible. And the materials you buy for a job are a cost only when matched against the income for that job, so do not double-count by claiming a deposit's materials twice.

Record-Keeping That Protects Your Refund

Conservatory work generates a lot of small documents: CIS statements, merchant receipts for glass and trims, fuel receipts, hire invoices for scaffold towers, and customer deposits paid in stages. Capture them as the job runs, not in a shoebox each January. The three records that matter most are your CIS deduction statements (your proof of tax already paid), your materials and tool receipts (your expense evidence), and your mileage log. Get those three right and the annual return, and the refund, look after themselves.

Worked Example: A Conservatory Installer on GBP 52,000

Take a subcontractor fitter invoicing GBP 52,000 for the year (GBP 44,000 labour, GBP 8,000 materials billed on), working under CIS for two glazing contractors.

Income: GBP 52,000

Allowable expenses:

• Van running costs and capital allowance: GBP 6,200
• Power tools and a new mitre saw (AIA): GBP 2,100
• Scaffold tower and ladder hire: GBP 900
• PPE, gloves and consumables: GBP 650
• Materials billed on to customers: GBP 8,000
• Public liability and tool insurance: GBP 750
• Phone, admin and accountancy: GBP 900
• Total expenses: GBP 19,500

Taxable profit: GBP 52,000 minus GBP 19,500 = GBP 32,500

Income Tax: GBP 32,500 minus GBP 12,570 = GBP 19,930 at 20% = GBP 3,986

Class 4 NIC: GBP 19,930 at 6% = GBP 1,196

Total tax and NIC: GBP 5,182. Now the CIS twist: 20% was deducted from the GBP 44,000 labour during the year, around GBP 8,800 already paid to HMRC. Against a GBP 5,182 bill, that points to a refund of roughly GBP 3,600 once you file. Run your own figures through the sole trader tax calculator and the CIS calculator to estimate your repayment.

VAT for Conservatory Installers

You must register for VAT once taxable turnover exceeds GBP 90,000 in any rolling 12-month period. Fitters hit this faster than most trades because supplying materials as well as labour inflates turnover quickly, so track your rolling 12-month figure every month. Most conservatory work for domestic customers is standard-rated at 20%, though some qualifying energy-saving glazing or certain new-build work can be reduced or zero-rated, so check the liability of each job rather than assuming.

If you subcontract labour to VAT-registered contractors, the construction domestic reverse charge usually applies: you do not add VAT to those invoices, the contractor accounts for it instead, and your invoice must say so. This trips up newly registered fitters who keep charging VAT on subcontract work they should be reverse-charging.

MTD for Income Tax: What Changes for Installers

Making Tax Digital for Income Tax replaces the once-a-year return with quarterly digital submissions and a year-end finalisation. The thresholds are based on gross income, not profit, and not your refund-adjusted figure:

• April 2026: Combined self-employment and property income over GBP 50,000
• April 2027: Over GBP 30,000
• April 2028: Over GBP 20,000

For a fitter who supplies materials, gross turnover climbs fast, so many will be in scope from April 2026 even when their profit is modest. The upside is real: recording each invoice, CIS statement and merchant receipt digitally as the job happens makes the year-end far less painful, and keeps your CIS refund evidence in order automatically. Our guide to MTD for sole traders shows what the quarterly rhythm looks like in practice.

Common Mistakes Conservatory Installers Make

Not registering for CIS. Staying unregistered means 30% deducted instead of 20%, tying up even more of your cash with HMRC until you file.

Losing CIS deduction statements. These are your proof of tax already paid. Without them your refund is hard to substantiate.

Mixing mileage and actual van costs. Pick one method per vehicle per year and stick to it; you cannot claim both.

Charging VAT on reverse-charge subcontract work. Once registered, subcontracted labour to VAT-registered contractors is usually reverse-charged, not VAT-charged.

Counting materials as income but forgetting them as cost. Materials you bill on are both, so record the cost against the same job to avoid overstating profit.

People also ask

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