Mortgage Agreement in Principle: The 2026 Guide

A mortgage Agreement in Principle (AIP) — also called a Decision in Principle (DIP) or a mortgage in principle — is a lender's written estimate of how much it would be prepared to lend you, based on a quick check of your income, outgoings and credit file. It is not a full mortgage offer and it does not guarantee you the money, but it shows estate agents that you are a credible, mortgage-ready buyer. Most AIPs use a soft credit check that leaves no visible mark, take minutes to obtain, and stay valid for roughly 30 to 90 days. In short: get one before you start making offers.

This guide explains exactly what an AIP is, how it differs from a full offer, whether it affects your credit score, how long it lasts, and how to get one — so you can house-hunt with a firm budget and negotiate from a position of strength.

What is a mortgage Agreement in Principle?

An Agreement in Principle is a lender's provisional indication of how much it might lend you. The lender takes a few basic details — your income, regular outgoings, deposit and address history — runs a check against your credit file, and returns a figure it is, in principle, willing to advance. The terms Agreement in Principle, Decision in Principle and mortgage in principle are used interchangeably by different lenders and brokers; they all mean the same thing. Crucially, it is an estimate, not a promise: the lender has not yet verified your income, valued a property, or committed to lend a single pound.

AIP vs a full mortgage offer — the key difference

The most common misunderstanding for first-time buyers is treating an AIP as though the mortgage is secured. It is not. An AIP is a preliminary sift; a full mortgage offer comes much later, after you have had an offer on a property accepted and submitted a complete application. Only at that stage does the lender verify your payslips and bank statements, run a hard credit search, and instruct a valuation of the specific property. If any of those checks throw up a problem — an unverifiable income source, an unexpected debt, or a down-valuation — the final offer can differ from, or fall short of, your AIP.

• Agreement in Principle — provisional estimate from a soft check; no property, no income verification, no legal commitment.
• Full mortgage application — submitted after an offer is accepted; income and deposit are verified and a hard credit search is run.
• Mortgage offer — the lender's formal, binding commitment to lend against a specific property, usually valid for three to six months.

Why estate agents want to see an AIP

Estate agents act for the seller, and their job is to sort serious buyers from browsers. An Agreement in Principle is the simplest proof that a lender is willing to fund a purchase in your price range, so many agents will ask to see one before they will book viewings or pass your offer to the seller. When two buyers offer the same amount, the one with an AIP — and ideally a mortgage broker lined up — almost always looks the safer bet. Having your AIP ready signals that your finances are in order and that the chain is less likely to collapse on your side.

Does an Agreement in Principle affect your credit score?

In most cases, no. The majority of lenders and brokers now use a soft credit check for an AIP. A soft search lets the lender see your credit history and confirm the figure, but it is only visible to you on your credit report and does not affect your score — you can run several without harm. A hard credit check is different: it leaves a footprint that other lenders can see, and making many hard searches in a short window can dent your score. A small number of lenders still run a hard search at the AIP stage, so always ask which type will be used before you proceed.

Soft check versus hard check at a glance

• Soft check — used for most AIPs; visible only to you; no impact on your credit score; safe to repeat.
• Hard check — used at full application (and occasionally at AIP); visible to lenders; multiple in quick succession can lower your score.
• Practical tip: confirm the search type first, and avoid scattering hard AIP requests across several lenders — a broker can do this once, for you.

How long does a mortgage Agreement in Principle last?

An Agreement in Principle is time-limited. Most last somewhere between 30 and 90 days, with 60 to 90 days being common, after which it simply expires. That is deliberate: your circumstances and the lender's rates can both change, so the estimate has a shelf life. If yours lapses before you have found a home, you can usually renew or reissue it, often with another soft check. Because rates in 2026 sit well above the lows of the early 2020s and can move quickly, it is worth timing your AIP so it stays live through your active house-hunting period rather than requesting it far too early.

How to get a mortgage Agreement in Principle

Getting an AIP is quick and free. You can apply directly with a lender online or, better for most first-time buyers, through a mortgage broker who can compare lenders and match you to one whose criteria fit your situation. Before you start, check your own credit report and correct any errors, and have your key figures to hand: gross income, regular outgoings and debts, your deposit amount, and three years of address history. The lender runs its check and, in many cases, returns a decision within minutes.

• Check your credit report first and fix any mistakes or outdated entries.
• Gather your income, outgoings, deposit figure and three-year address history.
• Decide whether to apply direct or through a broker — a broker widens your options.
• Confirm the lender uses a soft search so your credit score is protected.
• Keep the AIP document safe; you will show it to estate agents when you offer.

“An AIP tells you your realistic ceiling and tells the seller you are serious. It is one of the cheapest, fastest things you can do to strengthen your position — and one of the most overlooked.”

Common reasons an AIP is declined

A declined Agreement in Principle is not the end of the road, but it is a useful early warning. Common causes include a thin or damaged credit history, recent missed payments, too much existing debt relative to income, being newly self-employed without enough accounts, or simply applying to a lender whose criteria do not suit you. Because each lender scores applicants differently, a decline from one does not mean every lender will say no. This is exactly why getting your AIP early matters: it surfaces problems while you still have time to repair your credit or approach a lender that is a better fit.

This guide is for informational purposes only and does not constitute financial advice. Lending criteria, credit-check practices and validity periods vary by lender and by your individual circumstances — always speak to a qualified mortgage adviser before making decisions.