What a mortgage in principle actually tells you
A mortgage in principle gives you a realistic borrowing ceiling based on what a specific lender is willing to offer given your financial profile. It typically shows the maximum loan size they would consider, which combined with your deposit gives you a clear upper price limit for your property search. Shopping outside that range risks wasted viewings and disappointment.
However, a mortgage in principle is not a guarantee. The figure can change when the lender verifies your documents during a full application, and it can change again after the property is valued. A lender might offer £300,000 at the AIP stage and then reduce that once they see three years of bank statements showing irregular spending patterns or an undisclosed loan commitment. Similarly, if the property values below the agreed price, the loan-to-value changes and the offer may be adjusted.
Different lenders also use different affordability models. One lender might offer four times your salary while another offers 4.5 times, and the way they treat bonus income, self-employed drawings, or rental income from other properties varies considerably. A whole-of-market broker can identify which lenders are most likely to offer the largest and most competitive loan for your specific circumstances, which is why many buyers use a broker rather than applying directly.
Why to get a mortgage in principle before you start viewing
- It defines a realistic price range so you focus only on achievable properties.
- Estate agents and sellers take your offer far more seriously when you can demonstrate borrowing capacity.
- It surfaces credit problems or affordability shortfalls early, while you still have time to fix them before making an offer.
- Most lenders use a soft credit check at the AIP stage, so your credit score is unaffected.
- The information you provide speeds up the full mortgage application once an offer is accepted.
- Having an AIP strengthens your negotiating position in a competitive market.
What you will need to apply for a mortgage in principle
Have these details ready to get an accurate figure quickly:
- Proof of income: recent payslips (usually two to three months) if employed, or two to three years of accounts and an SA302 from HMRC if self-employed.
- Details of regular monthly outgoings, including any existing debts such as personal loans, credit cards, car finance or student loan payments.
- The size of your deposit and its source (savings, gift, Help to Buy or Lifetime ISA).
- Personal details including your National Insurance number.
- At least three years of address history, with dates at each address.
- Your employment details including employer name, salary and length of service.
How to get a mortgage in principle
1. Gather your documents
Collect payslips, bank statements or accounts, deposit evidence and your address history before you start. Having them to hand avoids abandoning the process halfway through.
2. Decide: direct lender or broker
Applying directly to one lender is quick but limits you to their products. A whole-of-market broker can assess dozens of lenders and find the right fit without multiple applications damaging your credit file.
3. Complete the application
Most online applications take 10 to 30 minutes. You declare income, debts and deposit, and the lender runs a soft credit check.
4. Receive your AIP certificate
If successful, you receive a written indication of the maximum loan amount. Many lenders provide a printable certificate to show estate agents.
5. Renew if it expires
AIPs typically last 30 to 90 days. If you have not found a property in that time, most lenders will renew it quickly with a further soft check.
Mortgage in principle vs full mortgage offer
These are two distinct stages in the mortgage process. Do not confuse them.
| Feature | Mortgage in principle (AIP) | Full mortgage offer |
|---|---|---|
| When obtained | Before house-hunting | After your offer on a property is accepted |
| Credit check type | Usually soft (no credit file impact) | Hard search (recorded on file) |
| Property valuation | Not required | Required; lender commissions a valuation |
| Income documents verified | No (self-declared) | Yes (payslips, bank statements, accounts checked) |
| Legally binding | No | Yes, subject to conditions |
| Time to receive | Minutes to one hour | Days to several weeks |
| Cost | Free | Valuation fee may apply (£150 to £400+) |
An AIP gets you into the property market. A full mortgage offer is what actually funds the purchase.
Hard vs soft credit checks: what is the difference?
A soft credit check retrieves a summary of your credit profile but is not recorded as a search on your credit file. Other lenders cannot see it, and it has no effect on your credit score. Most mortgage in principle applications use a soft check, which is why you can apply without concern during your property search.
A hard credit check is a full search recorded on your credit file and visible to other lenders for 12 months. Multiple hard searches in a short period can suggest to lenders that you are desperate for credit and may reduce your score temporarily. The full mortgage application always involves a hard check, so avoid making multiple full applications to different lenders simultaneously. This is another reason to use a broker: they identify the most suitable lender before you apply, reducing the need for multiple hard searches.
An AIP is not a guarantee of a mortgage
A mortgage in principle is based on self-declared information and a soft credit check. Your actual mortgage offer can differ once the lender verifies documents, runs a hard credit check and receives the property valuation. Common reasons for a reduced or declined full offer include undisclosed debts, irregular income patterns, a valuation below the purchase price, or a property the lender considers unsuitable. Do not commit to a purchase or pay non-refundable fees until you have a full mortgage offer in writing.