What Is a mortgage?
A mortgage is a loan secured against a property. The lender - usually a bank or building society - provides the funds to purchase the property. In return, you agree to repay that loan, plus interest, over a set number of years. Critically, the property itself serves as collateral: if you stop making payments, the lender has the legal right to repossess and sell the property to recover the outstanding debt.
This security is what makes mortgages possible at all. Because the lender can recover their money by selling the property if necessary, they are willing to lend large sums at relatively low interest rates compared to unsecured borrowing like personal loans or credit cards. A personal loan at £20,000 might charge 8-15% interest. A mortgage of £200,000 might charge 4-5% - the lower rate reflects the lender's security.
A mortgage is a secured loan used to buy property. The property is collateral - giving the lender security and you a lower interest rate. You repay the loan plus interest over a fixed term (typically 25-35 years). When fully repaid, you own the property outright with no encumbrances.
Equity vs Debt - How Ownership Builds Over Time
One of the most important concepts in understanding a mortgage is equity - the portion of the property you actually own. When you first buy a home with a mortgage, equity equals your deposit. As you make monthly payments, your loan balance reduces and your equity grows. Use the slider below to see how this changes over a 25-year repayment mortgage:
The Four Key Components of Every mortgage
Principal
The original amount borrowed - the loan itself. Each monthly repayment reduces the principal. As the principal falls, the monthly interest charge also falls.
Interest
The cost of borrowing - charged as a percentage applied to the outstanding principal each month. Higher balance = higher monthly interest charge.
Loan-to-Value (LTV)
Your mortgage as a percentage of the property's value. A £240K mortgage on a £300K home = 80% LTV. Lower LTV means better rates - lenders take less risk when your equity stake is larger.
Term
The number of years to repay the mortgage. Standard UK terms: 20-35 years. Longer term = lower monthly payments but much more total interest paid.
How Monthly mortgage Payments Are Calculated
Each monthly mortgage payment (on a repayment mortgage) covers two things: interest on the outstanding balance, and principal repayment that reduces the loan. The split between these two changes significantly over time - a concept called amortisation.
In the early years, the majority of each payment covers interest - because the outstanding balance is large. As the years pass and the balance falls, the interest portion decreases and the capital repayment portion increases.
| Year | Monthly Payment | Interest Portion | Principal Portion | Balance Remaining |
|---|---|---|---|---|
| Year 1 | £1,330 | £900 (68%) | £430 (32%) | £234,840 |
| Year 5 | £1,330 | £840 (63%) | £490 (37%) | £215,600 |
| Year 10 | £1,330 | £740 (56%) | £590 (44%) | £187,200 |
| Year 15 | £1,330 | £600 (45%) | £730 (55%) | £149,600 |
| Year 20 | £1,330 | £400 (30%) | £930 (70%) | £98,200 |
| Year 25 | £1,330 | £50 (4%) | £1,280 (96%) | £0 |
Illustrative figures: £240,000 mortgage at 4.5% over 25 years. Actual figures depend on exact rate and term.
Because early payments are mostly interest, making overpayments in the first years hits the principal directly - reducing the balance that all future interest is calculated on. A £10,000 overpayment in year 1 can save £15,000-£20,000 in interest over the life of a 25-year mortgage at 4.5%.
Repayment vs Interest-Only - The Critical Choice
Main Types of mortgage Rate
Fixed Rate mortgage
Your interest rate is guaranteed for a set initial period - typically 2, 3, or 5 years. Your monthly payment stays exactly the same regardless of what the Bank of England does. After the fixed period, you revert to the lender's Standard Variable Rate - at which point most people remortgage.
Variable Rate (Tracker)
Your rate tracks the Bank of England base rate plus a fixed margin. If the BoE cuts rates, your payment falls. If it raises rates, your payment rises. Often no early repayment charges - but monthly costs are unpredictable.
Standard Variable Rate (SVR)
The lender's default rate that applies after an initial deal period ends. Set entirely by the lender. Almost always significantly higher than competitive deals. Falling onto an SVR is the most common mortgage mistake.
Offset mortgage
Links your mortgage to a savings account. The savings balance "offsets" your mortgage balance - you only pay interest on the difference. Useful for higher-rate taxpayers as the benefit is tax-free.
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The mortgage Journey - From Application to Completion
Check Your Credit Report and Finances
Before approaching any lender, review your credit report (free at Experian, Equifax, or TransUnion), calculate your maximum deposit, and assess your income and outgoings.
Get a mortgage in Principle (MIP)
A lender or broker indicates how much they're likely to lend based on a soft credit check. This gives you a budget for property searching and shows sellers you're serious.
Find a Property and Make an Offer
Search within your confirmed budget, make an offer, and get it accepted. Once accepted, instruct a solicitor (conveyancer) to handle the legal side of the purchase.
Submit Full mortgage Application
Provide full documentation to your lender - payslips, bank statements, ID, proof of deposit. The lender assesses your affordability and creditworthiness.
Property Valuation and Survey
The lender commissions a valuation. Separately, you should commission an independent survey to check the property's condition. The valuation protects the lender; the survey protects you.
Receive Formal mortgage Offer
The lender issues a formal mortgage offer - a legally binding document confirming the loan amount, rate, term, and conditions. Review this carefully with your solicitor.
Exchange of Contracts
Both parties sign and exchange contracts, making the sale legally binding. You pay your deposit at this stage. Withdrawing after exchange incurs financial penalties.
Completion - You Get the Keys
Your solicitor transfers the remaining funds to the seller's solicitor. The property legally transfers to you. You collect the keys and the mortgage begins.