Remortgage maths: cash in pocket vs net wealth on a falling-rate refinance (UK 2026)
When a long fix becomes uncompetitive mid-term, most remortgage coverage poses the question as a single comparison: do the new monthly payments — over the remainder of the original fixed period — outweigh the Early Repayment Charge (ERC) paid to escape? If yes, refinance; if no, sit tight.
That framing leaves out half the answer. A lower rate kills more principal every month, so the borrower who refinances arrives at the end of the original fix horizon with a smaller outstanding balance. On a worked £300,000 loan at the Bank of England's April 2026 quoted 75% LTV 5-year fixed rate of 4.32%, the borrower whose raw cash flow is £1,592 worse off over the remaining 84 months of the fix is £1,162 better off once that lower end-of-fix balance is included.
The two numbers measure different things. Cash saving is what shows up in the current account month by month. Net wealth captures cash plus the gap between the two amortisation schedules — the principal each path leaves outstanding when the original fix would have expired. This piece sets out both numbers across three loan sizes and three rate-drop scenarios, so the choice can be framed against either yardstick.
The baseline
The worked example sits on the same baseline as our Early Repayment Charges and the falling-rate remortgage piece: a 10-year fix at a 4.85% sticker rate, 30-year amortisation, refinanced at the start of year four. The ERC schedule follows the standard high-street pattern of 5%/4%/3%/2%/1% in years one to five, so a year-3 break attracts a 3% ERC on the outstanding balance.
The refinance is modelled at three rate drops below the sticker: −50 basis points (4.35%), −75 bps (4.10%) and −100 bps (3.85%). −50 bps sits roughly at the April 2026 BoE 75LTV5Y print of 4.32% relative to the sticker. The new product is assumed fee-free and runs over the remaining 27 years of the original amortisation schedule. Cash and balance figures cover the remaining 84 months of the original fix.
| Loan | Old monthly | Balance at year 3 | Year-3 ERC (3%) | Old balance at year-10 end of fix |
|---|---|---|---|---|
| £200,000 | £1,055.38 | £190,447 | £5,713 | £161,944 |
| £300,000 | £1,583.08 | £285,671 | £8,570 | £242,916 |
| £400,000 | £2,110.77 | £380,895 | £11,427 | £323,888 |
The "old balance at year-10" column is the principal still owed at month 120 if the borrower stays on the 4.85% product to the end of the fix. It is the benchmark every refinance path is measured against.
What the numbers look like
For each scenario the table shows three figures. The raw cash saving is the difference between the old 84-month cash outlay and the new 84-month cash outlay plus the ERC. The balance differential is the gap between the year-10 balance on the old path and the year-10 balance on the refinanced path. Net wealth is the sum of the two.
| Loan | Rate drop | New rate | New monthly | Cash saving (84 mo) | Balance differential | Net wealth |
|---|---|---|---|---|---|---|
| £200,000 | −50 bps | 4.35% | £1,000.00 | −£1,061 | +£1,836 | +£775 |
| £200,000 | −75 bps | 4.10% | £972.89 | +£1,216 | +£2,783 | +£3,999 |
| £200,000 | −100 bps | 3.85% | £946.17 | +£3,460 | +£3,749 | +£7,209 |
| £300,000 | −50 bps | 4.35% | £1,500.00 | −£1,592 | +£2,754 | +£1,162 |
| £300,000 | −75 bps | 4.10% | £1,459.34 | +£1,824 | +£4,174 | +£5,998 |
| £300,000 | −100 bps | 3.85% | £1,419.26 | +£5,191 | +£5,623 | +£10,814 |
| £400,000 | −50 bps | 4.35% | £2,000.01 | −£2,123 | +£3,672 | +£1,549 |
| £400,000 | −75 bps | 4.10% | £1,945.78 | +£2,432 | +£5,566 | +£7,998 |
| £400,000 | −100 bps | 3.85% | £1,892.34 | +£6,921 | +£7,498 | +£14,419 |
Source: amortisation worked from HM Treasury / FCA standard mortgage maths; sticker 4.85% baseline; ERC at 3% on year-3 outstanding balance; refinance over remaining 27-year term, no fees. Calculation date: 6 June 2026.
The −50 bps row is the most informative. At every loan size the raw cash saving is negative — the borrower writes more cheques over the next seven years on the refinanced path than on the original — but the year-10 balance is materially lower because the new rate eats principal faster. The two effects net out positive, but most of the benefit lives inside the loan, not the current account.
Why the two numbers diverge
A mortgage payment is split between interest and principal repayment. At a lower rate, the interest portion shrinks and the principal portion grows. The total monthly payment also falls — that is the cash saving — but the share of each payment that reduces the loan balance climbs faster than the headline cut suggests. Over 84 months those extra principal repayments accumulate into the balance differential.
The cash saving is realised every month. The balance differential is realised only when the smaller balance is actually paid down or otherwise crystallised — typically when the original fix ends and the borrower either remortgages again, sells the property, or pays the loan off. Until that point the gap sits on the household balance sheet, not in the bank account.
That is the part standard ERC-breakeven coverage tends to skip. The breakeven point measured on cash flow alone gives one answer; the breakeven measured on net wealth gives another. At a 4.85%→4.35% drop on a £300k loan the cash answer says "no" and the wealth answer says "yes" — by a margin (£1,162) that is small enough to swing on any unmodelled cost.
What changes the picture
A few sensitivities to keep in mind. First, the ERC schedule above is the standard high-street five-year taper. Some long-fix products carry flat ERCs across the full fixed period; others (Habito One, April Mortgages, Perenna are examples of UK-market participants offering longer fixed structures) carry different schedules. The 3% figure is illustrative for year three under the standard pattern. The contract is the authority, not the table.
Second, the refinance modelled here assumes the new product is fee-free and runs over the remaining 27-year term. A £999 product fee added to the new loan principal pushes the break point higher and reduces both the cash and net-wealth numbers by roughly £1,000 plus the interest on that £1,000 over seven years. A new product on a fresh 30-year term would push cash saving higher (lower monthly payment, longer amortisation) but reduce the balance differential because more of each payment is interest, not principal.
Third, the cash-vs-balance gap narrows as the rate drop gets bigger. At −100 bps both numbers are firmly positive, and on net wealth the cash component is roughly half the total benefit. At −50 bps the cash component is negative and balance differential carries the whole result. The framing matters most where the rate move is modest — exactly the territory where the borrower has to decide whether the refinance is worth the friction.
Fourth, the FCA's rule on ERCs is that the charge must be a reasonable pre-estimate of the lender's costs of early redemption — set out in MCOB 12.3 of the Mortgage Conduct of Business sourcebook. The 5/4/3/2/1% taper is a common structure, not a regulatory minimum or ceiling. Borrowers refinancing should read the exact ERC clause in their facility letter rather than assume the headline number.
Why this matters in 2026
The BoE 75LTV5Y series tells the relevant story. The April 2026 print of 4.32% is the latest in a six-month run of falling quoted rates: 4.51% in November 2025, 4.48% in December, 4.42% in January 2026, 4.39% in February, 4.35% in March, 4.32% in April. That is a 19 bps fall over six months, the kind of move where the borrower on a 10-year fix taken at a higher sticker is right inside the band where the ERC math is non-trivial and the framing changes the answer.
A borrower who took a 4.85% 10-year fix in late 2024 sits ~53 bps above the current April 2026 quote — roughly the −50 bps row in the table above. On raw cash they are worse off refinancing today; on net wealth they are better off, but only by single thousands of pounds before any product fee or legal cost is included.
Three caveats:
- The future-rate path is unknown. The table compares the borrower's position as if the new rate held for the next seven years. If the new product is itself a shorter fix that resets in two or five years, the borrower is also taking a fresh rate-reset risk that the original 10-year product had insulated them from. The cycle 89 piece on Early Repayment Charges and the falling-rate remortgage treats this trade-off in more detail.
- Net wealth is not cash. A £1,162 net-wealth gain that lives entirely in a lower loan balance is real but not spendable. Borrowers facing cash-flow constraints reasonably attach more weight to the monthly figure than the balance figure.
- Affordability re-check. Any remortgage requires a fresh affordability assessment under FCA rules. The lower monthly payment on the new product is not automatic — the lender has to be willing to lend at all.
Worked example: a £300,000 loan, 4.85%→4.10%
Take the middle row: £300,000 loan, 4.85% sticker, refinanced at year three at 4.10%. The old monthly was £1,583.08; the new monthly is £1,459.34 — a saving of £123.74/month. Over 84 months that is £10,394 of monthly savings. Subtract the £8,570 ERC and the raw cash saving is £1,824.
The balance differential is larger. At month 120 on the original path the borrower owes £242,916. On the refinanced path the same month 120 balance is £238,742 — a £4,174 gap. The borrower is in for £1,824 of cash plus £4,174 of lower balance, for a £5,998 net-wealth result. The cash piece is 30% of the total; the balance piece is 70%.
To see the same calculation against your own price and deposit, open the mortgage comparison calculator with the £300k baseline pre-loaded and run the existing fix on one product line, the refinance on another. The Overpayments toggle on the refinance product line shows the same balance-differential mechanic in a different framing — overpayments and a lower rate both attack the principal share of each payment.
Where the table breaks down
A few cases where the worked numbers stop applying:
Short fixes. A two- or five-year fix where the borrower is mid-term still has the same mechanic, but the ERC schedule and the months-remaining of the fix are different. At year two of a 5-year fix the remaining horizon is 36 months and the ERC under the standard schedule is 4% — both numbers run the other direction (smaller balance differential because there is less amortisation time, but larger ERC drag because less of the fix has been "used up").
Interest-only loans. The entire framing collapses on an interest-only mortgage because there is no principal repayment to differentially accelerate. The cash saving is the only relevant number; the balance is the same under both paths until the bullet is paid.
Buy-to-let. Limited-company landlords and unincorporated landlords each get different tax treatments of the ERC itself — the cash and net-wealth figures both have a tax dimension a residential homeowner does not. See our piece on the limited-company landlord profit extraction tax stack for the corporate-side mechanics. Speak to a qualified tax adviser before treating a ERC as deductible.
Falling-rate scenarios after the affordability stress. A new product at a lower rate sometimes fails the lender's affordability check because the assessment is run at a stressed rate, not the new headline rate. The cash and net-wealth numbers are moot if the refinance application is declined.
How this fits into the broader picture
The cash-vs-balance distinction is one of the four assumption levers that most affect the buy-vs-rent decade-total calculation. The rate-stress test, the fix-length choice and the rent escalator are the other three; we cover them in the fix-length sensitivity buy-vs-rent piece. When the rate axis is read on a net-wealth basis rather than a cash basis it is materially less load-bearing than the cash framing suggests — the difference between a "no, don't refinance" and "yes, do" answer at −50 bps is roughly one product fee in size.
Browse the rest of our cost-intelligence guides for sibling pieces, or open a postcode-specific worked example at /?postcode=M1+1AE for the True Cost of a property in central Manchester at today's quoted rates.
Disclaimer
This is general information about how the maths works, not a recommendation. Mortgage and ERC terms vary between lenders, products and contracts; affordability rules, taxes and personal circumstances all change the answer. Speak to a qualified adviser before acting.
Based on a 4.85% baseline sticker rate, the standard 5/4/3/2/1% ERC taper, and the BoE 75LTV5Y April 2026 print of 4.32% (Bank of England quoted-rates dataset). All amortisation derived freshly for this article; no third-party model or estimator used. See our other cost-intelligence pieces for the methodology context.