Mortgage in principle (agreement in principle) explained
An agreement in principle (AIP), also called a decision in principle (DIP), is an early indication from a lender of roughly how much it might lend, based on a quick check of your income and credit. Some call it a mortgage in principle. It is not a mortgage offer and it is not guaranteed, but it shows sellers you are a serious buyer. Lenders differ on the credit check they use for it and on how long it lasts, so check before you apply.
What it is for
An AIP does two useful things. It gives you a realistic borrowing figure before you start viewing, so you shop in the right price range. And it reassures estate agents and sellers that an offer from you is credible. It is a quick, early step, not the full underwrite.
Soft check or hard check
Experian, one of the credit reference agencies, explains the difference. A soft check is "an initial look at certain information on your credit report", and soft searches "aren't visible to companies". A hard check is "a complete search of your credit report", and each one is recorded, so other lenders can see you have applied for credit. Experian says "most hard searches will stay on your credit report for 12 months" (Experian, searches and credit checks).
For an agreement in principle, Experian says "most lenders do what's called a 'soft' credit check", but that with some lenders it might affect your score (Experian, mortgage agreement in principle). Santander, for example, says its online decision in principle "is only a 'soft' search", and that it only does a hard search when you make a full mortgage application (Santander). Check what each lender says before you apply, especially if you plan to apply to more than one.
How to get an agreement in principle, step by step
- Check your credit file. You can ask any of the credit reference agencies for a free copy and get mistakes put right first. The ICO explains how.
- Gather your details. Lenders ask for things like your address history for the last 3 years, your income and outgoings, and any other borrowing such as credit cards or loans (Santander's list).
- Choose where to apply. You can apply to a lender directly or through a broker. It is your choice.
- Apply online or by phone. Nationwide says its decision in principle "takes around 20 minutes, lasts 90 days, and won't affect your credit score" (Nationwide). Ask each lender whether it uses a soft or hard credit check.
- Save the certificate. Keep the confirmation or download a copy, so you can show estate agents and sellers.
How long it lasts and which credit check: four lenders
| Lender | How long it lasts | Credit check | Source |
|---|---|---|---|
| Nationwide | 90 days | Soft check | Nationwide |
| Santander | 60 days | Soft search (online) | Santander |
| Yorkshire Building Society | 90 days | Not stated for its own DIP | YBS |
| Skipton Building Society | No expiry stated. You have 30 days to submit a full application after your DIP is accepted | Soft check | Skipton |
From each lender's own page, checked again on 22 October 2026. Lenders change these rules, so check the lender's page before you apply. We do not recommend any lender.
What it does not do
- It is not a mortgage offer, and it is not guaranteed. Experian says a lender giving you one is "not tied to the offer" (Experian).
- It does not value the property: that happens at full application.
- It is based on what you told the lender. At full application the lender checks your finances and the property in more detail, and can lend less or say no.
- It is a snapshot: a change in your circumstances can change the result.
- It runs out. Experian says they are "usually valid for between 30 and 90 days" (Experian). You can apply for a new one.
Common questions
What is an agreement in principle?
An agreement in principle (AIP), also called a decision in principle (DIP) or mortgage in principle, is an early indication from a lender of roughly how much it might lend you, based on a quick check of your income and credit. It is not a full mortgage offer, but it shows estate agents and sellers you are a serious buyer.
Does a mortgage in principle affect my credit score?
Usually not, but it depends on the lender. A soft check does not show to other lenders; a hard check is recorded on your credit file. The soft check or hard check section above explains the difference.
How long does a mortgage in principle last?
It depends on the lender. The table on this page shows how long it lasts at four lenders, taken from their own pages. If it runs out before you find a home, you can apply again, with the same lender or a different one.
How do I get a mortgage in principle?
Check your credit file, gather your income, outgoings and address history, then apply on a lender's website or through a broker. Ask whether they use a soft or hard credit check, and save the certificate so you can show it to estate agents.
Is an AIP a guarantee of a mortgage?
No. It is an indication, not an offer. The full application involves a deeper assessment, a property valuation and document checks, and the lender can still decline or lend less. Treat the AIP as a strong signal, not a certainty.
Next, see how much can I borrow and the documents you need.
Before you apply, use the mortgage documents checklist: the full application asks for proof of the income and outgoings you gave for the AIP.
Founder, MortgageExplained
Adam spent over eight years as a mortgage adviser at Just Mortgages, with further experience in commercial finance. He is CeMAP and CF qualified. He built MortgageExplained to do one thing well: explain mortgages in plain English, so you know where you stand before you speak to a regulated broker. Every page on the site is written by Adam.
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