What Is a Mortgage in Principle (MIP/AIP/DIP)?

A Mortgage in Principle — also called an Agreement in Principle (AIP) or Decision in Principle (DIP) — is a written indication from a lender of how much they may be willing to lend you. It is not a full mortgage offer and not a guarantee. This guide explains what one actually means, how it affects your credit score, how long it lasts, and how to get one without unnecessary risk.

What a Mortgage in Principle actually is

When you apply for a Mortgage in Principle, a lender takes a snapshot of your financial situation — your income, your regular outgoings, and a look at your credit history — and uses that to estimate how much they might be prepared to lend you. The process is typically quick: many lenders offer an online form with an instant or same-day response.

What you receive is indicative, not guaranteed. Here is what that means in practice:

• The figures are based entirely on what you tell the lender at that point, without any supporting documents.
• No formal underwriting takes place — no property valuation, no income verification, no deep-dive into your bank statements.
• Once you find a property and apply for a full mortgage, the lender will reassess everything from scratch. The amount they offer may differ from your MIP.

The table below shows how an MIP compares to a full mortgage offer:

Why getting a Mortgage in Principle matters

An MIP does two practical things for you as a buyer.

First, it gives you a realistic price range before you start viewing. Browsing properties significantly above what you can borrow is a common source of disappointment, and an MIP prevents that early on. Combined with working out what monthly repayments would actually look like, it keeps your search grounded.

Second, it signals to estate agents and sellers that you are a serious, proceedable buyer. Agents routinely ask for an MIP before they will pass an offer to a vendor, and in competitive markets some agents require one before accepting offers at all. Having one ready means you can move quickly when you find the right property.

One thing worth knowing: getting an MIP with one lender does not lock you to that lender. You can use it to support your offer and then choose an entirely different lender when it comes to your full mortgage application.

Hard vs Soft credit checks: will a Mortgage in Principle affect my credit score?

This is the question that worries buyers most. The short answer is: it depends on whether the lender uses a soft or hard credit check — and you should always ask before applying.

What is a soft credit check?

A soft check is a light-touch look at your credit file. The lender can see a summary of your credit history, but the check leaves no visible footprint for other lenders to see. It does not normally affect your credit score in any way. You can see soft checks on your own credit report, but they are invisible to anyone else.

Many UK lenders now use soft checks at MIP/AIP/DIP stage precisely because buyers want to explore their options without risk. If a lender confirms their MIP process uses a soft search, you can apply with confidence that your score will not be affected.

What is a hard credit check?

A hard check leaves a footprint on your credit file that other lenders can see. It records that you applied for credit at a particular date. A single hard check typically has a small, short-lived impact on your score — in isolation, it is unlikely to matter much.

The issue arises when multiple hard checks accumulate in a short period. Several hard-search MIPs in quick succession can cause a temporary dip in your score and may prompt underwriters to ask why you applied with multiple lenders — which can suggest earlier applications were refused, even if that is not the case.

How to protect your credit score

Before applying for any MIP, ask the lender directly: “Do you use a hard or soft credit search for a Mortgage in Principle?” Most will tell you clearly. If they use a hard search and you still want to proceed, be selective about where and when you apply.

Two scenarios to illustrate the difference:

• Scenario A: You apply for three MIPs over a few months, all with lenders that use soft searches. Your credit score is unaffected. Each lender can see your profile but leaves no mark visible to others. This is generally fine.
• Scenario B: You apply for three MIPs in quick succession with lenders that all use hard searches. Each one leaves a footprint. Taken together, they create a pattern that could cause a small, temporary dip and raise questions with a fourth lender.

One final point: whether or not your MIP involved a soft search, a full mortgage application always triggers a hard credit check. This is standard practice across every lender. The goal is to protect your score during the exploratory phase — not to avoid hard checks altogether.

What you need to get a Mortgage in Principle

Most lenders ask for the following information. In the majority of cases, you will not be asked to upload any documents at this stage — that comes later, at full application.

• Personal details: full name, date of birth, current address and contact details
• Address history: usually the last three years
• Employment status: employed, self-employed, contractor, or retired — plus employer name and start date if employed
• Income: salary, bonuses, overtime, commission, benefits, or — if self-employed — annual profit figures
• Existing credit commitments: personal loans, credit cards, car finance, student loan, Buy Now Pay Later, any maintenance payments
• Monthly outgoings: regular household costs, subscriptions, childcare
• Deposit: how much you have and where it is coming from (savings, gifted by family, inheritance, etc.)

The more accurate these figures are, the more reliable your MIP will be as a guide. Rounding up your income or underestimating your outgoings at this stage can mean the eventual full offer differs from what you expected.

How to get a Mortgage in Principle

There are three main routes, each with different trade-offs.

Online, direct with a lender

Most major UK lenders offer an online MIP application that takes around 15–20 minutes and gives an instant or same-day response. This is the quickest route, but you will only be assessed against that one lender's criteria.

Good for: buyers who already have a strong sense of which lender they want to use and want a fast result.

By phone or branch appointment

Some buyers prefer to talk through their situation before anything is submitted. A phone or in-branch appointment gives you the chance to ask questions and clarify details before the check runs.

Good for: people with a less straightforward income picture who want guidance before committing to an application.

Through a mortgage broker

A qualified, FCA-authorised broker can look across multiple lenders simultaneously, identify the ones most likely to accept your application, and help you avoid unnecessary hard searches or mismatches.

Good for: buyers with variable income, a small deposit, recent credit issues, or anyone who wants professional guidance without having to approach lenders directly. Brokers are regulated, which means you have formal protections if advice turns out to be wrong.

Whichever route you choose, the result is the same: a document or email from the lender confirming an indicative borrowing figure.

How long does a Mortgage in Principle last?

Most MIPs, AIPs and DIPs are valid for between 30 and 90 days, with 60–90 days being the most common window. The exact duration is set by the individual lender and will be clearly stated on the document or email they send you.

Once it expires, the MIP is no longer valid and cannot be shown to estate agents as evidence of your borrowing capacity. At that point, you have two options:

• Renew with the same lender — if your circumstances haven't changed significantly (same job, similar income, no new credit), renewal is usually straightforward. Soft-search lenders can typically re-run their check with minimal friction.
• Apply fresh — if your circumstances have changed, or you've decided to go with a different lender, a new application makes more sense.

One thing to be mindful of: if your original MIP involved a hard credit check, each renewal may trigger another one. This is less of a concern with soft-search lenders — but worth confirming before you renew.

What to do after you have a Mortgage in Principle

Getting your MIP is not the end of the process — it is the start of the active search phase. Here is the basic sequence from here:

1. Start viewing properties within the indicative budget your MIP confirmed. You now have a defensible price ceiling based on what a lender has assessed, not just a rough guess.
2. When you find a property you want to buy, make your offer and show your MIP/AIP/DIP to the estate agent as evidence that you are a proceedable buyer.
3. Once your offer is accepted, begin a full mortgage application with your chosen lender or through a broker. This is when full documentation is collected, a hard credit check runs, and a property valuation is commissioned.

For the full step-by-step journey from saving for a deposit to getting the keys, see our First-Time Buyer's Guide 2026.

Before you apply, use our Mortgage Affordability Calculator to sense-check how much you might be able to borrow and what monthly repayments could look like at different purchase prices.

Common Mortgage in Principle mistakes to avoid

• Applying for multiple MIPs with hard-search lenders in quick succession. Each one leaves a footprint. Even if the individual impact is small, the pattern can look concerning to underwriters.
• Treating your MIP as a guarantee. Lenders can and do reduce — or withdraw — their offer after full underwriting. Your MIP figure is an indication, not a promise.
• Letting your MIP expire mid-search. If you're actively house-hunting and your MIP lapses, you may need to reapply before an agent will process your offer. Keep an eye on the expiry date.
• Anchoring on the maximum amount the lender will give without checking the repayments. A lender may be willing to lend you more than is comfortable month to month. Use our Mortgage Repayment Calculator to see what those monthly figures actually look like before you commit to a budget.
• Not telling your lender or broker when your circumstances change. New job, pay rise, redundancy, a new credit card, or a change to your deposit — any of these can affect what you're offered. Flag changes before they surface at full application.

Frequently asked questions