Tax, CIS and Making Tax Digital for self-employed glaziers and window fitters

When Making Tax Digital starts for glaziers and window fitters

It depends on your qualifying income, not your trade. Qualifying income is the total of self-employment and property income before expenses (turnover), not profit.

Once you’re in, you send HMRC a quarterly update by 7 August, 7 November, 7 February and 7 May, then a tax return after the year ends. MTD for Income Tax does not change how tax is paid or the payment due dates.

Check your own start date and what to sort first. It’s free and takes a minute.

CIS for glaziers and window fitters

HMRC’s CIS guide lists installing and repairing glazing and doors as construction work, and its manual counts a conservatory on a foundation as a building. Making windows, doors or glazing materials and delivering them is excluded. A contract to supply and fit brings every payment under it into CIS, but the cost of the frames you bought or made is taken off before the deduction is worked out. Window film, blinds, curtains and louvred shutters are outside the scheme. Homeowners paying for work on their own home are not contractors, so they don’t deduct CIS.

When CIS applies, a contractor deducts 20% if you’re registered for CIS, 30% if you’re not, and nothing if you have gross payment status. To work out a CIS deduction, the contractor starts with the gross invoice and takes away what the subcontractor paid for VAT, consumable stores, fuel (except for travelling), plant hire, manufacturing or prefabricating materials, and materials; the CIS rate is then deducted from the amount left.

Before you join Making Tax Digital, over-deducted CIS is claimed back through your Self Assessment tax return. Once you are in Making Tax Digital, HMRC adds your CIS deductions to your tax return, and any refund is requested separately through HMRC online services. Either way, the sooner after 5 April the return is filed, the sooner HMRC can repay you.

Estimate your CIS refund

Free, and it runs in your browser: add your van or mileage, tools and phone, for 2025-26 and 2026-27.

Costs glaziers and window fitters usually claim

The test for every cost is whether it was for your business. If something is partly personal, only the business part counts.

Your van, tools and kit

Most window fitters go from home to a different job every day or two, which HMRC usually treats as business travel to temporary sites. If you make frames or units in a workshop and work from there, the trip from home to the workshop is commuting, and the miles from it to customers are business. Glass racks or an A-frame fitted to the van are business equipment, like the van itself. Large units often need a glazing robot or lifting gear for the day, and hiring it is a running cost.

From 2024-25 the cash basis is the default for sole traders and partnerships without corporate partners, with no turnover limit; traditional (accruals) accounting is an opt-out. Under the cash basis, the cost of equipment bought to keep and use in the business, such as machinery, computers and vans, is claimed as a normal allowable expense rather than a capital allowance. Cars are different: they go through capital allowances.

Simplified expenses for cars and goods vehicles (vans) from 6 April 2026: 55p a mile for the first 10,000 business miles, then 25p; motorcycles 24p. Once used for a vehicle you must keep using it for that vehicle, and it cannot be used for a vehicle already claimed through capital allowances.