Self-Employed Carpenter & Joiner
Tax & MTD Guide

If you are carrying out first-fix or second-fix carpentry on a building site as a sub-contractor, HMRC's Construction Industry Scheme means the contractor paying you is legally required to deduct 20% from your labour element before you ever see that money. On a site invoice of GBP 10,000 that includes GBP 7,000 labour and GBP 3,000 materials, the contractor withholds GBP 1,400 at source. That is not tax you owe; it is a payment on account that you reclaim or offset when you file your Self Assessment return. Many carpenters spend the year short of cash without understanding why.

Off site, the picture shifts. Private bespoke joinery jobs, kitchen fitting for homeowners, and shopfitting invoiced directly to clients sit outside CIS and are paid gross. The combination of CIS site work and gross private work is the defining cash-flow reality of this trade, and your tax return needs to reflect both streams clearly.

How Tax Works for a Self-Employed Carpenter

As a sole-trader carpenter your taxable profit is your total turnover minus allowable business expenses. That profit is taxed under Income Tax and also attracts Class 4 National Insurance Contributions.

For 2025/26 the key thresholds are:

So a carpenter with a taxable profit of GBP 35,000 pays 20% Income Tax on GBP 22,430 (GBP 35,000 minus the GBP 12,570 personal allowance) plus 6% Class 4 NIC on the same band. Every pound of allowable expense you claim reduces that taxable profit and cuts both bills simultaneously. Use the sole trader tax calculator to see your specific position before your return is due.

CIS: What It Means in Practice for Carpenters

CIS applies when you are working as a sub-contractor on a construction site for a contractor. It does not apply to direct jobs for homeowners or end clients who are not themselves contractors.

Once you are registered with HMRC as a CIS sub-contractor, the contractor deducts 20% from your labour-only element and pays it to HMRC on your behalf. If you are not registered, that deduction rises to 30%, so registration is non-negotiable. Materials you supply are deducted from the gross before the CIS rate is applied, which means a well-structured invoice that separates labour from timber and fixings costs you significantly less in deductions.

At the end of the tax year, the total CIS deductions appear on your Self Assessment return and are offset against your Income Tax and NIC liability. If the deductions exceed what you owe, HMRC refunds the difference, usually within a few weeks of filing. Use the CIS tax calculator to model your likely refund before you file.

Allowable Expenses for Carpenters and Joiners

This is where the tax return either saves you money or costs you it. The expenses below are the ones that appear on a working carpenter's books every month. Claim all of them; HMRC expects to see them.

Van Costs and the Mileage Decision

Most carpenters arrive at site in a van loaded with tools and materials. HMRC gives you two ways to account for that:

Flat-rate mileage: Claim 45p per mile for the first 10,000 business miles in the year, then 25p per mile beyond that. This covers fuel, servicing, insurance and depreciation in one figure. Use the mileage calculator to add up your annual claim before you file.

Actual costs: Add up every penny of fuel, insurance, road tax, servicing and repairs, then claim the business-use proportion. If you do 15,000 miles a year and 12,000 are business, your business proportion is 80%.

The critical rule: whichever method you choose, you must use it consistently for that vehicle throughout the tax year. Carpenters who switch from actual costs to mileage mid-year, or who apply the mileage rate on top of actual fuel costs, are claiming incorrectly. If you bought the van outright and are claiming actual costs, you will also claim the capital cost through the Annual Investment Allowance or writing-down allowances, not under running costs.

VAT and Bespoke Joinery: A Genuine Complication

Most carpentry work is standard-rated for VAT at 20%. But bespoke joinery that is supplied and fitted in a new dwelling being built from scratch can qualify as zero-rated, because it forms part of the construction of a new residential building. This is not a loophole; it is a specific HMRC provision in Notice 708.

In practice it means that if you are fitting bespoke units, staircase joinery or window frames in a new-build house, you may charge your contractor client 0% VAT on that work. If you are refitting a kitchen in an existing house, it is 20%. The distinction matters enormously once your turnover approaches the GBP 90,000 rolling threshold at which VAT registration becomes compulsory. A mix of zero-rated new-build work and standard-rated jobbing work can keep you under the threshold longer than you might expect, but you must track each supply accurately.

If you have not yet reached GBP 90,000 but are growing, build a 12-month rolling total into your bookkeeping every month. The threshold is crossed the moment your trailing 12-month turnover exceeds GBP 90,000, not at the end of the tax year.

Worked Example: Mixed CIS and Private Income

Take a carpenter turning over GBP 42,000 in 2025/26. GBP 26,000 comes from site work under CIS (labour and materials split 60/40, so GBP 15,600 labour and GBP 10,400 materials on the invoices). The remaining GBP 16,000 comes from private bespoke joinery jobs paid gross.

CIS deductions suffered during the year: Contractors deduct 20% of GBP 15,600 labour = GBP 3,120, paid to HMRC on this carpenter's behalf.

Calculating taxable profit:

Tax and NIC on GBP 25,100 profit:

• Income Tax: 20% on GBP 12,530 (profit minus personal allowance) = GBP 2,506
• Class 4 NIC: 6% on GBP 12,530 = GBP 752
• Total liability: GBP 3,258

Offset CIS deductions of GBP 3,120 against total liability of GBP 3,258. The balance owed to HMRC at Self Assessment: GBP 138, plus any Payment on Account instalment due for 2026/27.

Without claiming every legitimate expense, this carpenter's taxable profit would have been GBP 42,000 minus a token GBP 2,000 for materials, leaving GBP 40,000 taxable and a bill many times larger. Expense claims matter.

MTD for Income Tax: What Changes for Carpenters

Making Tax Digital for Income Tax (MTD for IT) is not optional and is not far away. From April 2026, self-employed people and landlords with combined income over GBP 50,000 must use HMRC-compatible software to submit quarterly digital updates. The GBP 30,000 threshold follows in April 2027.

For most self-employed carpenters this means:

• Four quarterly submissions per year summarising income and expenses, replacing one annual return.
• A final end-of-period statement and tax return at the end of the year.
• All records must be kept digitally from the start of the trading year.

If your turnover is currently around GBP 42,000 (as in the worked example), you are in the April 2027 cohort unless you also have rental income that takes your combined total above GBP 50,000. Either way, starting digital bookkeeping now means the April 2027 deadline arrives with 12 months of clean records rather than a shoebox. Read the full MTD for sole traders guide to understand exactly what the quarterly submissions involve and how TapTax automates the process.

Common Mistakes Carpenters Make on Their Tax Return

Claiming the whole of workshop or home-office costs without apportionment. This is the single most frequent error HMRC sees in carpenter tax returns. If you rent a separate commercial workshop from a landlord, the full rent is deductible. If you use a garage, outbuilding or room at home as a workshop, you must calculate the business-use proportion based on floor area and the hours it is used for work versus personal purposes. Claiming the entire mortgage interest or entire utility bill without an apportionment is incorrect and will draw HMRC attention during a compliance check.

Not separating materials from labour on CIS invoices. The CIS deduction only applies to the labour element. If your invoice lumps timber, fixings and labour into a single line, the contractor may deduct 20% of the whole amount. Breaking the invoice into materials and labour costs you nothing in administration and reduces the deduction immediately.

Missing the mileage log. If HMRC asks you to substantiate 12,000 business miles and you have no contemporaneous record, the claim fails. A simple spreadsheet, a mileage app, or TapTax's built-in tracking is enough. Start the log on 6 April and maintain it throughout the year.

Assuming all joinery VAT is standard-rated. Carpenters fitting bespoke joinery on new-build sites sometimes charge 20% VAT when the work qualifies for zero-rating. This overcharges the contractor client and creates unnecessary VAT accounting. Check Notice 708 or ask your accountant before invoicing.

Forgetting Payment on Account. Once your Self Assessment bill exceeds GBP 1,000, HMRC splits the following year's estimated liability into two advance payments due 31 January and 31 July. Carpenters who clear their first-year bill and then spend that money often find a second, unexpected demand arriving the same evening.

People also ask

Do self-employed carpenters have to register for CIS?

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What mileage rate can a self-employed carpenter claim for their van?

When does a self-employed carpenter need to register for VAT?