Last updated: 14 October 2026
Do you pay stamp duty if you buy your sister’s share of a property?
Possibly. Stamp Duty Land Tax (SDLT) is charged on the price you pay for your sister’s share, including any share of the mortgage you take over. There is no special family exemption. If the amount is above £125,000 (the residential nil-rate band in England and Northern Ireland), SDLT is due. The 5% higher rate for additional dwellings may apply if you own another home and the property won’t replace your main residence.
How the charge is worked out
SDLT is charged on the “chargeable consideration”. That is the cash you pay plus any debt you take on.
Example
You and your sister own a £400,000 house 50:50, with a £200,000 mortgage. You pay her £100,000 and take over her £100,000 share of the mortgage. Chargeable consideration is £200,000.
| Band | Rate | SDLT |
| £0 to £125,000 | 0% | £0 |
| £125,001 to £200,000 | 2% | £1,500 |
| Total | £1,500 |
If the higher rates for additional dwellings apply, each band is 5% higher: £10,000 + £1,500 = £11,500.
When the higher rates apply
The 5% surcharge can apply if you already own another residential property and the share you are buying isn’t a replacement for your main residence. There is a specific relief if you buy out a spouse, civil partner or co-owner of your main residence in some circumstances. Check the facts carefully, because these rules are detailed.
Gifts between siblings
If your sister gives you her share for nothing and there is no mortgage, there is no SDLT. If you take on her share of the mortgage, SDLT is due on that debt.
Capital gains tax for your sister
If the property isn’t her main home, your sister may have to pay CGT on the gain on her share, at 18% or 24%. Sales between siblings are treated as being at market value for CGT, even if you pay less. She must report and pay within 60 days.
Scotland and Wales
Scotland charges LBTT and Wales charges LTT, with different bands and surcharges.
Filing the return
Your solicitor files the SDLT return and pays the tax within 14 days of completion. A return is needed if the consideration is £40,000 or more.
Stamp duty mistakes on transfers
People often assume a gift is free of SDLT when the person receiving it takes on a share of the mortgage. The mortgage share counts as payment, and SDLT may be due if it’s over the threshold. Transfers between spouses are also caught when debt is taken on. If a return is needed, file it within 14 days.
Frequently asked questions
Is there first-time buyer relief?
Not usually, if you already co-own the property, because you are not a first-time buyer.
Does SDLT apply to inherited shares?
No. See stamp duty on inherited property.
What if I pay less than market value?
For SDLT, tax is on what you actually pay plus any debt you take on. For your sister’s CGT, market value applies.
Can I reclaim the surcharge later?
If you sell your previous main home within 3 years, you may be able to claim a refund of the higher rates.
Related: capital gains on a property gift.
Talk to Accotax
Want this handled for you? Our team at Accotax can help with stamp duty on property transfers. See our property tax accountants service, or contact us for a free, no-obligation quote.
This page is general guidance based on HMRC rules for the 2026/27 tax year, checked against gov.uk on 14 October 2026. It is not personal advice, so speak to an accountant about your own situation.
