What is a mortgage agreement in principle?

Last reviewed 8 July 2026 · Compare Mortgage Rates editorial team

This guide looks at the topic through a rate-comparison lens, with emphasis on total cost, eligibility and lender criteria rather than headline rates alone.

An Agreement in Principle (AIP) — sometimes called a Decision in Principle (DIP) — is a lender’s indication that they’d be willing to lend you a specified amount, based on the information you’ve given them. It’s not a full mortgage offer.

Why you need one

Most estate agents won’t put your offer forward without an AIP. It shows you’re a credible buyer.

What it’s based on

Your stated income and outgoings.
Deposit size and source.
A soft (usually) credit search.
The lender’s current affordability model.

How long it lasts

Usually 30–90 days, depending on the lender. You can renew it if your search takes longer.

Soft vs hard search

Most lenders run a soft search for an AIP — it’s only visible to you on your credit file. A small minority run a hard search; always check before consenting.

The AIP is not the offer

The full mortgage offer comes after underwriting, document checks, and a property valuation. AIPs can still be declined at full application stage if circumstances change.

Frequently asked questions

Is an agreement in principle the same as a mortgage offer? +

No. An agreement in principle is an indication based on initial information. A full mortgage offer only follows underwriting, document checks, and a property valuation.

Can an agreement in principle be declined later? +

Yes. A lender can still decline a full application if the details, documents, credit file, property, or lender criteria do not support the application.