Buying Property from a Family Member: SDLT on Connected Party Deals
When you buy from a family member at a discount, SDLT is still charged on the open market value, not the price you paid. The connected party rule under s.53 FA 2003 applies.
Last verified: April 2026
Key Takeaways
- •Under s.53 FA 2003, SDLT is charged on open market value when buyer and seller are connected, regardless of the actual price paid.
- •"Connected" includes spouse/civil partner, parent, child, sibling, and their spouses, as well as companies under common control.
- •An outright gift with no mortgage means chargeable consideration of £0 and no SDLT is due.
- •If you take over an outstanding mortgage on a gifted property, SDLT is charged on the mortgage debt assumed.
- •Underreporting the chargeable consideration on a connected party sale carries penalties. HMRC risk-assesses these returns.
In this article
The Connected Party Rule
Section 53 of the Finance Act 2003 provides that where a land transaction is between connected persons, the chargeable consideration for SDLT purposes is taken to be not less than the open market value of the subject-matter of the transaction.
In plain terms: if a parent sells a house to their child for £300,000, but the property is worth £400,000 on the open market, SDLT is calculated on £400,000, not £300,000. The actual cash price paid is irrelevant where connected parties are involved and the price is below market value.
If the price paid is at or above market value, s.53 has no additional effect. SDLT is calculated on the price paid in the normal way. The rule only bites when there is a discount.
It is worth understanding why this rule exists. Without it, families could avoid SDLT almost entirely by selling at well below market value. Parliament closed that loophole by anchoring the tax base to market value in connected party deals, ensuring the tax charge reflects the economic reality of the property being transferred, not the artificially low price agreed between relatives.
Statutory reference: Finance Act 2003, s.53. "Where a land transaction is entered into by a person as purchaser (alone or jointly) in connection with the acquisition of an interest in land by a connected person, the market value rule applies."
Who Counts as Connected?
The definition of "connected person" for SDLT purposes follows s.1122 of the Corporation Tax Act 2010. The key connected relationships for family property transactions are:
| Relationship | Connected? |
|---|---|
| Spouse or civil partner | Yes |
| Parent or child | Yes |
| Sibling (brother or sister) | Yes |
| Lineal ancestor or descendant (grandparent, grandchild) | Yes |
| Spouse or civil partner of the above relatives | Yes |
| Unmarried cohabiting partner | No |
| Friend or acquaintance | No |
| Companies under common control | Yes |
Unmarried partners are NOT connected: The connected person rules do not extend to cohabiting (unmarried) partners. A transaction between unmarried partners at a discounted price is not subject to the market value rule. SDLT is charged on the actual consideration paid.
Worked Examples
Parent sells to child at a discount
Scenario: Parent sells house to child for £300,000. Open market value assessed at £400,000. The connected party rule applies: SDLT is charged on £400,000.
| Basis | Consideration | SDLT Due |
|---|---|---|
| Price paid (what you might expect) | £300,000 | £5,000 |
| Open market value (s.53 FA2003) | £400,000 | £10,000 |
Extra SDLT due to the connected party rule: £5,000. This is charged on the buyer even though they paid only £300,000.
SDLT on £400,000: 0% on £0 to £125k = £0; 2% on £125k to £250k = £2,500; 5% on £250k to £400k = £7,500. Total: £10,000.
What this means in practice
The child in this scenario pays £10,000 in SDLT on a property they purchased for £300,000. They did not receive £400,000 worth of consideration in cash terms, but HMRC still charges them as though they did. The discount from the parent is effectively treated as a gift of equity, and the buyer is liable for the full SDLT on the market value. This surprises many families who assume SDLT is simply based on the amount of money that changes hands.
Gifted Property and Mortgages
When a family member gifts a property outright (with no cash consideration and no outstanding mortgage) the chargeable consideration is £0. No SDLT is due, regardless of the property's market value.
However, if the gifted property carries an outstanding mortgage that the recipient takes over, the assumed debt becomes the chargeable consideration. SDLT is charged on the amount of the mortgage debt assumed, even though no cash changes hands.
This catches many families off guard. A parent wanting to help their child onto the property ladder by gifting them a flat assumes that because no money is exchanged, there is no tax to pay. If there is still a mortgage on the property, the child is acquiring that debt as part of the deal, and HMRC treats the debt as the chargeable consideration. The same logic applies to equity release products: if the property has a lifetime mortgage or other secured debt, taking that over triggers SDLT on the outstanding balance.
Gift with £150,000 outstanding mortgage
| Band | Rate | Tax |
|---|---|---|
| £0 to £125,000 | 0% | £0 |
| £125,000 to £150,000 | 2% | £500 |
| Total SDLT on assumed mortgage debt | £500 | |
Chargeable consideration = £150,000 (the mortgage debt assumed). Market value of the property itself is irrelevant because no cash was paid and only debt was assumed.
Pure gift (no mortgage)
£0
No consideration, no SDLT
Gift with £150k mortgage assumed
£500
SDLT charged on assumed debt
What to Disclose
The SDLT land transaction return must accurately reflect the chargeable consideration. Where the connected party rule applies, the chargeable consideration is the open market value, not the price paid. The return must therefore show the market value figure.
HMRC risk-assesses SDLT returns and is alert to transactions between connected parties at a discount. A return showing a low consideration for a connected party transaction, with no explanation, is likely to attract scrutiny. HMRC may raise a compliance check and request a surveyor's valuation.
Even if you believe the discount was modest and the risk of an enquiry is low, it is always better to report accurately from the outset. If HMRC does open a compliance check years later, finding that you understated the chargeable consideration will result in interest on the underpayment plus potential penalties. The cost of an accurate RICS valuation at the time of purchase is small compared to the exposure of getting it wrong.
Penalties for underreporting: An incorrect SDLT return that understates chargeable consideration can attract a penalty of up to 30% of the unpaid tax (or 100% for deliberate concealment), plus interest on the underpayment. Always obtain a professional valuation when a connected party transaction involves any discount.
Best practice: Commission a RICS-qualified surveyor to provide a formal market valuation at the date of completion. Attach this to your records and use the surveyor's figure as the chargeable consideration in the SDLT return.
Common Mistakes to Avoid
Family property transactions produce more SDLT errors than almost any other type of purchase. The informal nature of deals between relatives leads buyers to underestimate the complexity of the rules. These are the mistakes that come up most often.
Mistake 1: Calculating SDLT on the discounted price rather than market value
This is the most common error. A buyer whose parent sells them a £400,000 property for £300,000 instructs their solicitor to pay SDLT on £300,000. The solicitor (especially if inexperienced in connected party transactions) may do exactly that. The correct calculation is on the market value of £400,000. If this error is discovered by HMRC, the buyer faces back-tax, interest, and potentially a penalty.
Mistake 2: Assuming a "love and affection" transfer avoids SDLT
Some older guidance and online forums suggest that a transfer "for love and affection" is free of SDLT. This is only true if there is genuinely zero consideration (no cash, no mortgage, no debt). If any debt is assumed or any payment made, SDLT is due on that consideration. The phrase has no legal effect on the SDLT calculation.
Mistake 3: Forgetting about the additional dwelling surcharge
If the buyer already owns another property (even one they are living in), the 5% additional dwelling surcharge applies on top of the standard rates calculated on the market value. Many people focus on the market value adjustment and forget that the surcharge also applies. In the example above, if the child already owns a property, SDLT is not just £10,000 on the market value: it is calculated at the higher rates including the 5% surcharge.
Mistake 4: Not getting a formal valuation
Families often use an informal estimate of market value, perhaps based on Rightmove comparables, rather than commissioning a RICS valuation. HMRC can challenge an informal estimate far more easily than a formal surveyor's report. Spending a few hundred pounds on a professional valuation protects you against an HMRC enquiry and provides a defensible basis for the figure used in the SDLT return.
Forum Spotlight
These are representative questions drawn from UK property forums, including r/HousingUK and MoneySavingExpert. The answers reflect the rules as they stand in April 2026.
Someone asked on a UK property forum:
"My parents want to sell me their house for £50,000 less than it is worth so I can afford to buy it. My solicitor says I owe SDLT on the full market value. Is that really right?"
Yes, unfortunately that is exactly right. Section 53 of the Finance Act 2003 specifically addresses this scenario. Because your parents are connected persons (under the Corporation Tax Act 2010 definition), the chargeable consideration for SDLT is the open market value, not the price agreed between you. Your solicitor is correct to calculate SDLT on the full market value.
The good news is that the discount itself is not taxed in any other way at the time of purchase (though your parents may have Capital Gains Tax considerations if the property has increased in value since they bought it). From a pure SDLT perspective, you pay as if you bought at market value, regardless of what actually changes hands.
Someone asked on a UK property forum:
"My gran wants to give me her flat. It is worth about £180,000 and still has a mortgage of £40,000 on it. How much SDLT do I owe?"
When you take over your grandmother's mortgage, the £40,000 outstanding debt becomes the chargeable consideration for SDLT purposes. On £40,000, SDLT is nil (the threshold is £125,000 at standard rates). So in this case, you would pay no SDLT at all, provided the only consideration is the assumed mortgage debt.
However, you need to be aware that if you already own a property, the additional dwelling surcharge applies to the assumed mortgage debt as consideration. Even at £40,000, the surcharge might apply at 5%, giving an SDLT charge of £2,000. Check your situation with your solicitor before assuming the figure is zero.
Someone asked on a UK property forum:
"I am buying my parents' house at full market value. They want to immediately gift me a sum of money to use as a deposit. Does HMRC see through this arrangement?"
If you are genuinely paying full market value for the property and the gift is a separate financial arrangement, the connected party rule does not change your SDLT position, because you are paying market value in any case. The SDLT is correctly calculated on the market value price you are paying. The fact that your parents are simultaneously gifting you money does not affect the SDLT on the purchase, as long as the two transactions are genuinely independent. If the gift is structured in a way that effectively reduces the net price paid, HMRC could argue otherwise. Keep the transactions clearly separate and document both.
Someone asked on a UK property forum:
"My brother and I are not speaking and I am buying his share of our jointly-inherited property. We agreed a price below what a surveyor said it was worth. Do the connected party rules apply?"
Yes, siblings are connected persons under s.1122 CTA 2010. Even if you are not on good terms, the legal relationship means the connected party rules apply. SDLT is calculated on the open market value of his share, not the discounted price you agreed. The fact that there is a dispute or that the discount was not a favour but a settlement does not change the statutory position. You should commission a RICS valuation of the share being transferred and use that figure in your SDLT return.
Frequently Asked Questions
How does HMRC know if my family sold below market value?
SDLT returns are risk-assessed. Large discounts between connected parties are a common audit trigger. HMRC may request a valuation or challenge a return. Using a certified surveyor's valuation at the date of purchase is advisable.
Does the connected party rule apply to unmarried partners?
No. Unmarried cohabiting partners are not "connected persons" for SDLT purposes. The connected party rules apply to legal family relationships and business connections, not romantic relationships.
My parents want to gift me their second home. How much SDLT will I pay?
If the property has no outstanding mortgage and is gifted outright, the chargeable consideration is £0, meaning no SDLT. If there's a mortgage you take over, SDLT is charged on the debt assumed.
Can I avoid the market value rule by using a trust?
No. Transfers into and out of trusts involving connected persons are subject to the same market value rules. HMRC actively challenges artificial structures designed to circumvent the connected party provisions.
Reviewed by
Emma Richardson, MRICS
Chartered Surveyor & Property Tax Specialist
Emma Richardson is a RICS-qualified Chartered Surveyor with over 12 years of experience in UK property taxation. She founded Calculate My Stamp Duty UK to help buyers understand the complex world of property transaction taxes.