Agreement in Principle (AIP)

An Agreement in Principle (AIP) is exactly the same thing as a Decision in Principle (DIP). Different lenders simply use different names for the same process. You may also hear it called a Mortgage in Principle (MIP). Regardless of the label, it means a lender has reviewed your basic financial details and indicated how much they would be prepared to lend you.

Why the different names?

There is no regulatory reason for the different terminology — it is simply a branding choice. Barclays might call it a DIP, while Halifax calls it an AIP. The underlying process is identical: you provide your income, deposit, and basic details, the lender runs a credit check (usually a soft search), and they tell you the amount they would consider lending in principle.

This can be confusing when you are speaking to multiple lenders or reading advice online. If someone mentions a DIP, AIP, or MIP, they are all referring to the same preliminary approval step that comes before a full mortgage application.

What an AIP does and does not guarantee

An AIP is not a binding mortgage offer. It confirms that, based on the information you have provided, the lender is willing to lend a certain amount. The full application process involves verifying your income with payslips and bank statements, a detailed credit check, and a valuation of the property you want to buy. The final offer may differ from the AIP amount.

That said, an AIP is genuinely useful. Estate agents take buyers more seriously when they can show an AIP, and it gives you confidence in your budget before you start viewing properties. Most AIPs last around 90 days, after which you would need to reapply.

Last updated: April 2026