What is a mortgage agreement in principle?

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.