UK Mortgage Cashback Calculator
Compare cashback mortgage deals against lower-rate alternatives. Find your break-even point, understand clawback risk if you remortgage early, check the tax treatment, and calculate the total package value including free valuation and legal fees. All figures in GBP.
UK cashback mortgages typically pay the cashback either at legal completion or 3 months after completion. The delay has a small but real cash flow cost — especially if you need the funds to cover moving costs immediately.
Mortgage cashback received from a UK lender is treated as a reduction in the cost of the mortgage, not as taxable income. HMRC confirmed this position in guidance — cashback incentives on residential mortgages are capital in nature and do not form part of your assessable income.
This means you keep the full £1,000 — you do not need to declare it on your Self Assessment tax return and you will not pay Income Tax or National Insurance on it, regardless of whether you are employed, self-employed, or a higher-rate taxpayer.
How to Use the UK Mortgage Cashback Calculator
Enter your mortgage amount, the cashback on offer, the rate with the cashback deal, and the rate on the equivalent non-cashback deal. The calculator shows you total cost over the full term, which deal is cheaper at 2-year and 5-year hold, and the break-even point where the cashback stops offsetting the higher rate.
What Is a Cashback Mortgage?
- Cash incentive: The lender pays you a lump sum (typically £500–£2,000) at or shortly after completion
- Higher rate trade-off: Cashback deals almost always carry a slightly higher interest rate to fund the incentive
- Clawback clause: Most cashback deals require repayment if you remortgage within 2–3 years
- Not taxable: HMRC confirms residential mortgage cashback is not taxable income
The True Cost of a Cashback Mortgage
A cashback deal can be cheaper or more expensive than a lower-rate deal depending on your loan size, the rate difference, and how long you hold the mortgage. The key calculation is:
Net cost without cashback = Monthly payment × months
Break-even = Cashback ÷ monthly payment difference
Example (£250,000 mortgage, 25-year term):
Deal A: 4.20% with £1,000 cashback → £1,350/mo → cost at 2yr = £31,400 net
Deal B: 3.90% no cashback → £1,310/mo → cost at 2yr = £31,440
Break-even: £1,000 ÷ £40/mo = 25 months
→ Cashback deal wins after 25 months (just over 2 years)
Clawback Rules Explained
Most UK cashback mortgages include a clawback provision — if you repay the mortgage early (by remortgaging to another lender or selling and not porting), you must repay the cashback in full. This is distinct from an Early Repayment Charge (ERC) and applies even after the fixed period has ended, up to the clawback expiry date.
Typical clawback scenarios
| Scenario | Clawback Applies? |
|---|---|
| Remortgage to new lender within 2 years | Yes — full cashback repaid |
| Sell house and repay within 2 years | Often yes — check your offer |
| Product transfer (stay with same lender) | Usually no |
| Remortgage after clawback period | No — cashback is yours to keep |
Always check the exact clawback terms in your mortgage offer document — the trigger events and period vary by lender.
Cashback vs Lower Rate: When Each Wins
Whether cashback beats a lower rate depends on how long you hold the deal and your loan size. The higher the loan and the shorter the holding period, the more likely cashback wins.
£1,000 cashback + 4.2% vs 3.9% no cashback on a £250,000 mortgage
| Hold Period | Cashback Deal Total | No-Cashback Total | Winner |
|---|---|---|---|
| 1 year | £15,200 | £15,720 | Cashback (saves £520) |
| 2 years | £31,400 | £31,440 | Cashback (saves £40) |
| 3 years | £47,600 | £47,160 | No-cashback (saves £440) |
| 5 years | £80,000 | £78,600 | No-cashback (saves £1,400) |
The break-even is approximately 25 months. If you plan to remortgage at a 2-year fix, cashback wins. If you plan a 5-year fix, the lower rate wins.