Buying process
Mortgage Agreement in Principle: what it is and how to get one
5 min read · Updated June 2026
An Agreement in Principle — also called a Mortgage in Principle, Decision in Principle, AIP or DIP, depending on which lender you ask — is a statement from a lender saying how much they would probably lend you, based on a quick check of your income and credit profile.
It is not a mortgage offer and it guarantees nothing. But it's the difference between an estate agent treating your offer as real and treating it as noise — and it takes about 15 minutes to get.
What it actually tells you
- Roughly how much a lender is willing to lend you — which, with your deposit, sets your realistic budget
- That nothing in your credit profile causes instant rejection
- That you're a serious, mortgage-ready buyer — the thing agents and sellers actually care about
What it doesn't tell you: that you'll get the loan. The full application involves hard checks, documentary proof of income and a valuation of the specific property. AIPs get declined at full application stage often enough that you should never treat one as certainty.
How to get one
- Pick a route: directly with a lender (most banks do it online in minutes) or through a mortgage broker (who will also tell you which lender suits your circumstances — usually the better first move)
- Provide basics: income, regular outgoings, deposit size, employment status, address history
- The lender runs a credit check — for most lenders a soft check that leaves no mark on your credit file, but a minority still run hard checks, so ask first
- You get a certificate, usually valid for 30–90 days, stating the indicative amount
Does it affect your credit score?
Usually not — most lenders use soft searches for AIPs. A soft search is visible only to you, not to other lenders. Hard searches (used in full applications, and by a few lenders even at AIP stage) are visible and, in volume, lower your score. The practical rule: ask whether the check is soft before proceeding, and don't collect AIPs from many lenders in the same month for fun.
When to get it
Before you book your first viewing — genuinely. It costs nothing, sharpens your budget from “about £300k?” to a number, and means that when the right house appears you can offer the same day with evidence in hand. Agents increasingly ask for it before arranging viewings at all.
If it expires before you find a place, renewal is the same 15-minute exercise. If your circumstances change — new job, new car loan, bigger deposit — get a fresh one; the old number is stale.
The short version
- An AIP is a lender's indicative “yes, probably, about this much” — not a guarantee
- Takes ~15 minutes, online or via a broker; usually a soft credit check only
- Get it before you start viewing — agents take offers with an AIP far more seriously
- Valid 30–90 days; refresh it if it lapses or your finances change
- The full mortgage application is a separate, deeper process — an AIP is the rehearsal, not the performance
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