Getting a mortgage pre-approval is the single most useful step you can take before you start viewing homes seriously. It tells you exactly how much a lender is prepared to offer you, it proves to estate agents and sellers that you are a serious buyer, and it stops you falling in love with homes that were never within your budget in the first place.
Yet many buyers skip it, or leave it until after they have found a home — by which point delays can cost them the property. This step-by-step guide explains what a mortgage pre-approval actually is, what lenders check, the documents you will need, and the common mistakes that slow buyers down.
What Is a Mortgage Pre-Approval?
A mortgage pre-approval — often called an Agreement in Principle, Decision in Principle or Mortgage in Principle in the UK — is a lender’s conditional statement of how much they would be willing to lend you, based on a check of your income, outgoings and credit history.
It is not a guarantee: the lender still needs to value the specific property and complete full underwriting before a formal mortgage offer. But it is far more than a guess from an online calculator. Estate agents know the difference, and in a competitive market, a buyer with a pre-approval is usually taken more seriously than one without.
Step 1: Check Your Credit Report First
Before any lender looks at your credit file, look at it yourself. Check all three main UK credit agencies for errors, old addresses and any missed payments you did not know about. Mistakes can be corrected for free, and fixing them before you apply is far easier than explaining them during an application.
While you are there, avoid taking new credit in the months before applying. A new car finance agreement or credit card reduces the amount lenders calculate you can afford, and can delay or reduce your pre-approval.
Step 2: Work Out Your Deposit and Budget
Your deposit size decides which deals you can access. In general, deposits step up in bands — 5%, 10%, 15%, 25% and beyond — and each bigger band usually unlocks better rates because the lender’s risk is lower. If you are close to the next band, waiting a little longer to cross it can be worth more than rushing.
Alongside the deposit, budget honestly for the full cost of buying: stamp duty, solicitor fees, survey costs, moving costs and an emergency fund for the home itself. A pre-approval based on realistic numbers is one you can actually use.
Step 3: Gather Your Documents
Lenders ask for evidence of everything, and gathering it in advance is the fastest way to speed up the whole process:
- Proof of ID and address — passport or driving licence, plus recent utility bills or bank statements.
- Proof of income — usually your last three months of payslips and your most recent P60 if you are employed.
- Bank statements — normally the last three months, showing your salary going in and your spending going out.
- Proof of deposit — statements showing the money saved, or a letter confirming a gifted deposit from family.
- Self-employment evidence — if you work for yourself, expect to show two to three years of accounts or tax returns.
Step 4: Choose How to Apply
You can apply directly to a bank or building society, or through a mortgage broker. A broker searches across many lenders, knows which ones suit first-time buyers, self-employed applicants or people with imperfect credit, and handles the paperwork with you. Many brokers are paid by the lender, not by you. Whichever route you choose, you will answer detailed questions about your income, debts, dependents and spending.
Step 5: Understand the Affordability Check
Lenders do not simply multiply your salary. They stress-test your finances: could you still afford the mortgage if rates rose? They examine regular spending — childcare, travel, subscriptions, debts — and they run a credit check. Some pre-approvals use a soft credit search, which other lenders cannot see; a full application normally uses a hard search, which leaves a mark on your file. Ask which type will be used before you agree.
Step 6: Receive and Use Your Pre-Approval
If successful, you will receive a certificate or letter stating the amount you can borrow in principle and how long it is valid — commonly 30 to 90 days. Take it to viewings. When you find the right home, your pre-approval lets you make an offer immediately and confidently, with your full mortgage application following once the offer is accepted.
Mistakes That Delay or Damage a Pre-Approval
- Applying everywhere at once. Multiple hard credit searches in a short period can lower your score. Get advice first, then apply once, properly.
- Moving money around without a paper trail. Large unexplained deposits into your account will be questioned. Keep statements that show where the money came from.
- Underestimating your spending. Lenders will see your real outgoings in your statements. Honest numbers get faster, cleaner decisions.
- Letting it expire before you buy. Note the expiry date. Renewing a pre-approval is normal, but an expired one at offer stage looks unprepared.
The Bottom Line
A mortgage pre-approval costs nothing but a little organisation, and it changes how every seller and agent treats you. Check your credit file, gather your documents, understand what you can truly afford, and get your pre-approval in place before the viewings begin. It is the closest thing buying a home has to a head start.
Frequently Asked Questions
How long does a mortgage pre-approval take?
With your documents ready, many lenders issue a pre-approval within a few days, and some within 24 to 48 hours. Self-employed applicants or complex incomes usually take longer.
Does a pre-approval affect my credit score?
A soft-search pre-approval does not affect your score and is invisible to other lenders. A hard search leaves a mark for a period of time, which is why it pays not to make lots of full applications at once.
How long is a mortgage pre-approval valid?
Typically 30 to 90 days depending on the lender. If it expires before you buy, you can usually renew it, although the lender may repeat some checks.
Is a pre-approval a guarantee I will get the mortgage?
No. It is a strong indication based on your circumstances. The final decision also depends on the lender’s valuation of the property and full underwriting of your application.
