A mortgage in principle — also called an agreement in principle (AIP) or decision in principle (DIP) — is a statement from a lender saying they'd be willing to lend you up to a certain amount, based on the information you've given them. It's conditional, not guaranteed. But it's an important early step.
Why you need one before you start viewing
Estate agents use the AIP as a filter. When you call to book a viewing on a property you're serious about, many agents will ask: "Do you have a mortgage in principle?" If you don't, some will still book the viewing, but they may deprioritise you when it comes to communicating offers or updates.
More importantly, an AIP clarifies your actual budget. You might think you can afford £250,000, but the lender might only be comfortable with £210,000. Better to know before you spend weekends viewing properties you can't buy.
What information you'll need
Getting an AIP typically takes 20–30 minutes online. You'll need:
- Your income (salary, self-employed earnings, or other income)
- Your outgoings (existing debts, credit commitments, regular expenses)
- Employment status and history
- Your deposit amount and source
- Basic personal details for the credit check
Soft vs hard credit checks
This is the question most first-time buyers don't think to ask.
Soft credit search: The lender looks at your credit file, but it's invisible to other lenders. You can get as many soft search AIPs as you like without affecting your score. Most high street lenders and mortgage brokers now use soft searches for the AIP stage.
Hard credit search: The lender's enquiry is recorded on your credit file and visible to any lender who checks it in the future. Several hard searches in a short period can lower your credit score and make you look like you're desperately seeking credit. A small number of hard searches is fine, but be selective.
If you're unsure which type a lender uses, ask them directly or check their website before applying.
How long an AIP lasts
Most AIPs are valid for 60–90 days. Some are as short as 30 days. You'll usually see the expiry date on the AIP document.
If yours expires before you find a property, you can renew it — most lenders will do this quickly. If your circumstances have changed (new job, change in income, new debt), make sure the updated information is accurate.
What an AIP is not
An AIP is not a mortgage offer. It's an early-stage indication. When you find a property and submit a full application, the lender:
- Verifies everything you told them (payslips, bank statements, P60s)
- Instructs a valuation of the property
- Checks the property itself is acceptable as security
Any of these can change the outcome. The full offer is the commitment. The AIP is a signal.
What to do if you're declined for an AIP
Being declined is worth taking seriously. Common reasons include:
- Credit score too low — check your credit report for errors, defaults, or missed payments
- Income doesn't meet affordability — the lender's calculation doesn't support the amount you've asked for
- Employment status — some lenders are more restrictive with contractors or the newly self-employed
- Too many existing debts — credit cards, car finance, student loans all affect affordability
If declined, don't immediately apply to multiple lenders. Each hard search adds to your file. Instead, get a copy of your credit report, understand the reason, and speak to a mortgage broker who can identify which lenders are most likely to accept your circumstances.
This guide is information only. Dom does not provide financial, mortgage or legal advice. Always consult a qualified mortgage adviser before making mortgage decisions.