What an agreement in principle is
An agreement in principle (AIP), also called a decision in principle (DIP), is a lender's indication of how much it might lend you, based on a quick check of your income, outgoings and usually a soft credit search. It's a strong signal of what you can borrow — but it isn't a guarantee or a formal mortgage offer.
Getting one is quick and usually free, whether directly with a lender or through a broker. It gives you a realistic budget before you start offering, so you don't fall for a home you can't fund.
AIP versus a full mortgage offer
The full mortgage offer comes later, after you've made a full application and the lender has carried out underwriting and a valuation of the specific property. That's a more rigorous stage, and things about the property itself can still affect it.
Issues a pre-offer check can surface — a flood-risk location, a very low EPC, a listed building, a short lease, or Japanese knotweed near the house — are exactly the things that can make a lender add conditions or decline at the valuation stage. Knowing them before you offer helps you avoid a deal that falls apart at underwriting.
How long it lasts and the credit impact
An AIP typically lasts somewhere between 30 and 90 days, and can usually be renewed if your search takes longer. Most use a soft credit check that doesn't affect your score, but a few lenders use a hard search — so confirm which before you apply if you're making several.
Avoid collecting lots of hard credit checks in a short space of time, as that can dent your score. A broker can help you target the right lender first time rather than scattering applications.
Why it strengthens your offer — and what to pair it with
Estate agents and sellers strongly favour buyers who already hold an AIP, because it shows you're serious and able to proceed. In a competitive situation it can be the difference between offers, and it speeds up the move to a full application once your offer is accepted.
Pair your AIP with a pre-offer check on the property itself, so you're confident in both the financing and the asset before you commit. If you'd like help finding the right deal — especially for a tricky property like a listed building or non-standard construction — TrueBrick can introduce you to an FCA-authorised mortgage broker who searches the whole market.
Frequently asked questions
Is an agreement in principle a guarantee I'll get the mortgage?
No. It's an indication based on a light check. The full mortgage offer depends on a complete application, underwriting and a valuation of the specific property — which can still throw up conditions or a decline.
Does getting an AIP affect my credit score?
Usually not — most lenders use a soft search for an AIP, which isn't visible to others. A minority use a hard search, so check first, and avoid making lots of hard-checked applications close together.
How long does an agreement in principle last?
Commonly 30 to 90 days, and it can normally be renewed. If your property search runs longer, refresh it so it's current when you make an offer.