Stamp Duty Refund Calculator Methodology

What this calculator does

Takes the purchase price of the new property (where the higher rate SDLT was paid), and calculates the refund due once the previous main residence is sold within the qualifying window.

The formula

Higher rate SDLT paid = standard SDLT + additional dwelling surcharge (5%)

Refund = Additional Dwelling Supplement element only
       = purchase price × 5%

Eligibility conditions:
  1. You paid the higher rate SDLT at purchase.
  2. You have since sold your previous main residence.
  3. The sale occurred within 36 months of the purchase
     (or longer if delayed by COVID, court order, or other specified reasons).
  4. The property being refunded was intended as your main residence.

Claim deadline: 12 months after the date of sale of the previous main residence,
or 12 months after the filing date of the original SDLT return — whichever is later.

Standard SDLT bands (1 April 2025 onwards)

£0 – £125,000:          0%
£125,001 – £250,000:    2%
£250,001 – £925,000:    5%
£925,001 – £1,500,000: 10%
Above £1,500,000:       12%

Additional dwelling surcharge: 5% on the full purchase price

Assumptions

The user confirms that all eligibility conditions are met — the calculator does not independently verify them.
The refund amount is the ADS element (5% of purchase price) only; the standard SDLT remains payable.
Applies to England only.

Data sources

Figure	Value used	Source	Last checked
ADS rate	5%	HMRC — SDLT higher rates for additional dwellings	May 2026
Refund window	36 months	HMRC — SDLT higher rates refunds	May 2026
Claim deadline	12 months after sale	HMRC — SDLT: refund for additional dwellings	May 2026

Limitations

Does not verify eligibility — the user must confirm all conditions are met before submitting a claim to HMRC.
Does not model the overlap period rules for property chains.
Does not cover Scotland (LBTT ADS rules differ slightly) or Wales (LTT has separate rules).

Worked example

Bought new property for £400,000 whilst still owning the old home, paid higher rate SDLT. Sold old home 8 months later.

Standard SDLT on £400,000:
  0% on £0–£125,000        = £0
  2% on £125,001–£250,000  = £125,000 × 2% = £2,500
  5% on £250,001–£400,000  = £150,000 × 5% = £7,500
  Standard SDLT             = £10,000

ADS surcharge: £400,000 × 5% = £20,000
Total SDLT paid: £30,000

Refund (ADS element): £20,000
Net SDLT after refund: £10,000

Changelog

Date	Change
May 2026	Initial publication

Use the Stamp Duty Refund Calculator →

Stamp Duty Refund Calculator — Methodology