Do joint buyers pay higher SDLT if only one is replacing their main residence?

Introduction

This is a common Stamp Duty Land Tax question for unmarried couples and other joint buyers. One person may be selling their home and buying a new one, while the other already owns another dwelling and is not selling a main residence. The key issue is whether adding that second person to the title of the home being sold can avoid the higher rates of SDLT on the new purchase.

In most cases, the answer is no. The higher rates rules for additional dwellings are applied strictly, and joint purchasers are generally treated as a single unit for SDLT purposes.

The Question

Two unmarried individuals want to buy a new home together. One of them owns a buy-to-let property. The other owns a current home, which will be sold at the same time as the new purchase, and also owns another investment property.

They are considering transferring a share of the current home into the other partner’s name before the sale, with that person also taking on a share of the existing mortgage. They want to know:

• whether SDLT would be payable on that transfer of equity, and
• whether doing this would allow the new joint purchase to qualify for the ordinary residential rates rather than the higher rates for additional dwellings.

Nick’s Explanation

Nick’s core view was that the transfer of equity itself may not trigger SDLT if the incoming owner only assumes a relatively small share of the mortgage, but that this does not solve the higher-rates problem on the new purchase.

In anonymised form, his reasoning was:

• Where a person is added to a property title and takes on part of an existing mortgage, that assumed debt counts as chargeable consideration for SDLT.
• If the amount of debt assumed is below the relevant SDLT threshold, no SDLT may be payable on the transfer of equity itself.
• However, for the new home purchase, the replacement of main residence exception only helps a buyer who is actually replacing their own only or main residence.
• If the other joint buyer already owns another dwelling and is not disposing of a main residence of their own, that buyer is still caught by the higher rates rules.
• Because joint purchasers are tested together, if one of them is caught by the higher rates, the surcharge applies to the whole purchase.

Nick also explained that simply being added to the title of the home being sold does not by itself make that property the incoming owner’s only or main residence for SDLT purposes.

The Law

SDLT is charged under the Finance Act 2003. The main provisions relevant here are these:

• Finance Act 2003, s.55 sets out how SDLT is charged and the rate structure for residential transactions.

• Finance Act 2003, Schedule 4, paragraph 8 provides that where a purchaser assumes liability for existing secured debt, such as a mortgage, that debt assumption counts as chargeable consideration.

• Finance Act 2003, Schedule 4ZA contains the higher rates for additional dwellings.

• Schedule 4ZA, paragraph 3 deals with when the higher rates apply to an individual purchaser.

• Schedule 4ZA, paragraph 3(6) contains the replacement of only or main residence exception.

• Finance Act 2003, s.103 contains joint purchaser rules, under which the buyers are effectively tested together for SDLT purposes.

The broad effect of these rules is:

1. If someone acquires an interest in a property and takes on part of the mortgage, that mortgage share is treated as consideration.
2. If a buyer owns another dwelling at the end of the day of the transaction, the higher rates may apply unless an exception is available.
3. The replacement exception only applies where that buyer is disposing of a dwelling that has been their only or main residence.
4. On a joint purchase, if one buyer fails the test and is subject to the higher rates, the whole transaction is charged at the higher rates.

Analysis

The position can be worked through in two stages.

First, the transfer of equity into the existing home.

If one partner is given a share of the other partner’s home and takes responsibility for part of the outstanding mortgage, the amount of mortgage debt taken on is chargeable consideration. If, for example, the share of debt assumed is £33,600, that is the figure tested for SDLT on the transfer. On the figures described, that amount would not itself produce an SDLT liability because it falls below the relevant threshold.

Second, the later joint purchase of the new home.

This is where the planning fails. The partner who is selling their current home may be replacing their only or main residence, so they may fall within the exception in Schedule 4ZA paragraph 3(6). But the other partner is in a different position. If that person already owns another dwelling and is not disposing of a property that has been their own only or main residence, they are still buying an additional dwelling for SDLT purposes.

Adding that person to the title of the current home shortly before sale does not automatically make that property their only or main residence. SDLT looks at the real factual position, not just legal ownership. If the property has not genuinely been that person’s only or main residence, the replacement exception does not become available merely because they were put on the title.

Because the new home is being bought jointly, the joint purchaser rule then matters. Under section 103, if one joint buyer is caught by the higher rates, the higher rates apply to the entire acquisition. In practical terms, that means the whole purchase price of the new home is charged using the higher residential rates.

So there are really two separate answers:

• the transfer of equity may produce little or no SDLT by itself, depending on the mortgage debt assumed; but
• it does not usually remove the higher rates charge on the later joint purchase.

Outcome

On these facts, transferring a share of the existing home to the other partner before sale is unlikely to achieve the hoped-for SDLT result on the new purchase.

The likely outcome is:

• no SDLT, or only limited SDLT, on the transfer of equity itself if the assumed mortgage debt is below the threshold; but
• the higher rates of SDLT still applying to the new joint purchase, because one buyer owns another dwelling and is not replacing their own only or main residence.

So the proposed step is not generally an effective way to secure ordinary residential rates on the new home.

Practical Steps

If you are assessing a similar situation, work through these points carefully:

1. List every dwelling each buyer owns or has a major interest in on the effective date of the new purchase.

2. Identify whether each buyer is disposing of a dwelling that has genuinely been their only or main residence.

3. Do not assume that being added to a title shortly before sale is enough to satisfy the replacement test.

4. If there is a transfer of equity before the purchase, calculate the exact mortgage debt being assumed, because that is the starting point for any SDLT charge on that transfer.

5. Apply the joint purchaser rule to the new purchase. If one buyer is within the higher rates, assume the whole transaction may be charged at those rates unless a clear statutory exception applies.

6. Check the SDLT rates in force on the effective date of the transaction, as rate bands and surcharges can change.

Conclusion

Where two people buy a home jointly, the higher rates cannot usually be avoided simply by adding one buyer to the title of the other buyer’s existing home before it is sold. The crucial question is whether each buyer is truly replacing their own only or main residence. If one is not, the higher rates will normally apply to the whole purchase.

Legal References Used

• Finance Act 2003, s.55
• Finance Act 2003, s.103
• Finance Act 2003, Schedule 4, paragraph 8
• Finance Act 2003, Schedule 4ZA
• Finance Act 2003, Schedule 4ZA, paragraph 3
• Finance Act 2003, Schedule 4ZA, paragraph 3(6)

This page was last updated on 22 March 2026.

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