Is a Granny Annexe VAT-Free in 2026? (UK)
It depends entirely on whether HMRC treats your annexe as a new self-contained dwelling or as an extension to your existing home. A genuinely separate annexe — its own entrance, kitchen and bathroom, that could be sold or let independently and isn't tied by a planning condition to the main house — can be zero-rated by a contractor or reclaimed through the DIY Housebuilder Scheme. An annexe that's connected to and dependent on your home is standard-rated at 20%, with no reclaim. The distinction is worth thousands, so this guide explains exactly where the line sits and how to claim if you qualify.
Planning the work? Check what it usually costs, or work out your own estimate. The free quote form is at the top of this page.
When a Granny Annexe Is VAT-Free
To be zero-rated as a new dwelling, an annexe generally must meet all of these:
- Self-contained living — its own kitchen, bathroom and sleeping space.
- Separate independent entrance, not only accessible through the main house.
- Capable of separate use, sale or letting — no internal-only connection that makes it part of the main home.
- No planning condition preventing separate disposal or tying its use to the main dwelling.
- Lawfully built with the correct planning permission for a new dwelling.
Fail any one — most commonly the “separate use” test, because a planning condition ties the annexe to the main house — and the build is standard-rated at 20%.
Zero-Rating vs the DIY Housebuilder Scheme
- Using a VAT-registered contractor: if the annexe qualifies as a new dwelling, the builder zero-rates their invoices — you simply don't pay the 20% in the first place.
- Building it yourself / managing trades: you pay VAT as you go, then reclaim it through HMRC's DIY Housebuilder Scheme. As of 2026 the claim is made online and must be submitted within 6 months of completion.
- Eligible costs: building materials incorporated into the dwelling and qualifying contractor services. Pure professional fees (architect, surveyor) and most appliances/furniture are not reclaimable.
- Keep every invoice — HMRC requires valid VAT invoices and the completion certificate to process the claim.
Detached, Attached or a Conversion — How the VAT Differs
The VAT treatment follows what you are actually building, not what you call it. Three situations come up again and again:
- A new, self-contained detached annexe — 0%. If it is a genuine new dwelling that passes the separate-use test, a contractor can zero-rate the build, or a self-builder can reclaim the VAT through the DIY Housebuilder Scheme.
- An attached or internal annexe — 20%. If it is really an extension of your existing home — sharing access and tied to the main house — it is standard-rated, like any other extension.
- Converting an existing outbuilding — often 5%. Turning a barn, garage or other non-residential building into living space, or changing the number of dwellings on the plot, can qualify for the reduced 5% VAT rate on the contractor's work. This route is easy to overlook and can save a lot against the 20% rate.
The definitive rules are set out in HMRC VAT Notice 708. Before you commit, it is worth reading how to build a granny annexe, checking whether a garden room is VAT-free if that suits you better, and lining up a builder using our guide to choosing an annexe builder.
Common Questions
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