Mortgage on £550K House in London

Buying a House in the UK: Two Costs You Must Know

This calculator combines the two most critical numbers every UK buyer needs before making an offer: 1. Monthly Mortgage Repayments — what you owe the lender every month for the life of the loan 2. Stamp Duty Land Tax (SDLT) — a one-off tax paid to HMRC on completion, often tens of thousands of pounds

Getting both wrong is the most common reason first-time buyers are caught short at exchange.

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How Your Monthly Repayment Is Calculated

UK mortgages use the standard amortisation formula. For a £315,000 loan** (£350,000 property, £35,000 deposit) at **5.5% over 25 years:

| Input | Value | |---|---| | Loan amount | £315,000 | | Annual interest rate | 5.5% | | Monthly rate | 0.4583% | | Term | 300 months | | Monthly repayment** | **£1,929 |

Over 25 years you repay £578,700** total — **£263,700 in interest on top of your £315,000 principal. Every percentage point of interest rate matters enormously at UK property prices.

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Stamp Duty Land Tax (SDLT) — 2026/27 Rates

SDLT is a progressive slab tax — different rates apply to different portions of the purchase price.

Standard Rates (Home Movers)

| Property Price Portion | SDLT Rate | |---|---| | Up to £250,000 | 0% | | £250,001 – £925,000 | 5% | | £925,001 – £1,500,000 | 10% | | Over £1,500,000 | 12% |

First-Time Buyer Relief

First-time buyers pay 0% up to £425,000 and 5% from £425,001 to £625,000. Properties over £625,000 do not qualify for relief — the standard rates apply in full.

Example — First-Time Buyer buying £450,000 property:

• £0 to £425,000 → £0 (0%)
• £425,001 to £450,000 = £25,000 × 5% → £1,250
• Total SDLT: £1,250 (vs £10,000 under standard rates — a saving of £8,750)

Additional Dwelling Surcharge

If you already own a residential property anywhere in the world, a 3% surcharge is added to every band. A buy-to-let investor buying a £350,000 property pays:

• Standard SDLT: £5,000
• Surcharge (3% × £350,000): £10,500
• Total: £15,500

LTV — Why Your Deposit Size Changes Everything

Loan-to-Value (LTV) is the percentage of the property price you are borrowing. Lenders tier their best rates to lower LTV bands.

| LTV Band | Typical 2-Year Fix | Risk Profile | |---|---|---| | 60% LTV (40% deposit) | ~4.5–4.8% | Best rates available | | 75% LTV (25% deposit) | ~4.8–5.1% | Good rates | | 85% LTV (15% deposit) | ~5.2–5.6% | Above average | | 90% LTV (10% deposit) | ~5.5–6.0% | Higher risk tier | | 95% LTV (5% deposit) | ~5.9–6.5% | Limited lender choice |

Moving from 90% to 85% LTV by saving an extra 5% deposit can reduce your rate by 0.3–0.5%, saving thousands over a 2-year fixed term.

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UK Mortgage Types Explained

Repayment Mortgage (Capital + Interest) Each monthly payment reduces your balance and pays interest. You are guaranteed to own the property outright at the end of the term if you never miss a payment. This is the standard type recommended by the FCA for most buyers.

Interest-Only Mortgage You pay only the interest each month — the capital balance never reduces. You must have a separate repayment vehicle (ISA, pension, investments) to repay the full loan at term end. Typically restricted to buy-to-let landlords or high-net-worth residential borrowers.

Fixed-Rate Mortgage Your interest rate is locked for a set period (2, 3, or 5 years are most common). Protects against Bank of England base rate rises. At the end of the fix, you revert to the lender's Standard Variable Rate (SVR) — usually 1–2% higher — so remortgaging before the fix ends is critical.

Tracker Mortgage Rate moves directly in line with the Bank of England base rate (e.g., BoE base + 1.0%). If the base rate is 4.75%, you pay 5.75%. Offers transparency but no protection against rate rises.

Offset Mortgage Your savings account is "offset" against the mortgage balance, so you only pay interest on the net amount. If you have a £200,000 mortgage and £30,000 in savings, you pay interest on £170,000. No interest earned on savings, but you reduce mortgage interest (often taxed at marginal rate) — effective for higher-rate taxpayers.

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The Bank of England Base Rate and Your Mortgage

The BoE base rate directly influences tracker mortgages and indirectly drives fixed-rate pricing through SONIA swap rates. As of March 2026, the base rate is 4.50% following a series of cuts from the 2023 peak of 5.25%.

Lenders price 2-year fixed rates roughly at: *Base Rate + 0.5% to 1.5%* depending on LTV and market competition. When the MPC signals rate cuts, fixed rates typically fall in anticipation — which is why locking in during a cutting cycle can be advantageous.

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Affordability Stress Testing

The FCA's mortgage affordability rules (updated post-2022) require lenders to stress-test your repayments at rates typically 3% above the reversion rate (SVR). Even if you pass at today's rate, lenders check whether you could still afford payments if rates rose sharply.

Income multiple limits**: Most lenders cap at **4.5× gross annual income**, though some specialist lenders extend to 5× or 5.5× for professionals (doctors, lawyers, accountants). At 4.5× income, a household earning £70,000 combined can borrow up to **£315,000.

| Combined Income | 4.5× Maximum Loan | 5× Maximum Loan | |---|---|---| | £50,000 | £225,000 | £250,000 | | £70,000 | £315,000 | £350,000 | | £90,000 | £405,000 | £450,000 | | £120,000 | £540,000 | £600,000 |

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Help to Buy and Shared Ownership

Shared Ownership: You buy a share of the property (25%–75%) and pay subsidised rent on the remainder to a housing association. You can "staircase" up to 100% ownership over time. SDLT is calculated only on the share you purchase initially (unless you opt for the market value method).

Lifetime ISA (LISA): Save up to £4,000/year and receive a 25% government bonus (up to £1,000/year). Must be used for a first home costing £450,000 or less, or withdrawn penalty-free at age 60+.

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Cash Required on Completion: The Full Picture

Most first-time buyers underestimate total upfront costs. For a £350,000 purchase with 10% deposit:

| Cost | Amount | |---|---| | Deposit | £35,000 | | Stamp Duty (FTB) | £1,250 | | Solicitor / conveyancing fees | £1,500–£3,000 | | Survey (HomeBuyer Report) | £400–£900 | | Mortgage arrangement fee | £0–£2,000 | | Removals | £500–£2,000 | | Total cash needed** | **~£39,650–£44,150 |

Budget at least 2–3% of the purchase price on top of your deposit for transaction costs.

Curious about how much you'll actually keep each month in London? We're here to make the numbers easy to understand.

Official rates for London are subject to yearly adjustments.