Before you view a single property in the UK, most estate agents will ask whether you have a mortgage in principle (also called an agreement in principle or decision in principle). It's one of the first hurdles in the home-buying journey, and understanding what it actually is — and isn't — can save you time, disappointment and unnecessary credit checks.
What is a mortgage in principle?
A mortgage in principle (MIP) is a statement from a lender or broker confirming, in theory, how much they might be willing to lend you based on a quick assessment of your income, outgoings and credit history. It is not a formal mortgage offer and it is not legally binding on either side. Think of it as a lender saying "on the information you've given us, we'd probably lend you around this much" rather than "we will definitely lend you this."
Most lenders can issue a mortgage in principle within minutes online, asking for details such as your annual income, employment status, any dependants, existing credit commitments, and the deposit you have available.
Why estate agents ask for one
Selling agents use a mortgage in principle as a basic filter to check that a prospective buyer is a realistic, serious purchaser before arranging viewings or accepting an offer. In competitive markets, sellers are far more likely to accept an offer from a buyer who can prove they're mortgage-ready.
- It demonstrates you've thought about affordability before falling in love with a property.
- It speeds up the process once you find a home, because much of the initial data-gathering is already done.
- It can strengthen a negotiating position, particularly against buyers who haven't taken this step.
Soft search vs hard search: protecting your credit score
This is the detail most first-time buyers get wrong. Some lenders use a soft search (or "soft footprint") to generate a mortgage in principle, which doesn't affect your credit score and isn't visible to other lenders. Others use a hard search, which leaves a visible mark on your credit file.
How long does a mortgage in principle last?
Typically a mortgage in principle is valid for 60 to 90 days, though this varies by lender. If your house-hunting takes longer than that, you'll usually need to request a fresh one — which is generally straightforward as long as your circumstances haven't materially changed.
What information do you need?
| Information | Why it's needed |
|---|---|
| Gross annual income (and partner's, if joint) | Used with income multiples to estimate borrowing |
| Employment status | Employed, self-employed, contractor status affects assessment |
| Deposit amount | Determines your likely loan-to-value (LTV) |
| Existing credit commitments | Loans, credit cards and car finance reduce affordability |
| Credit history summary | Flags any missed payments, defaults or CCJs |
Common misconceptions
A mortgage in principle is not a guarantee. Once you find a property and submit a full mortgage application, the lender will carry out a much more detailed assessment — verifying your income with payslips or accounts, running a full credit check, and instructing a valuation of the property itself. It's entirely possible, though relatively uncommon, for a full application to be declined or offered at a lower amount even after a positive mortgage in principle, particularly if your circumstances have changed or the property doesn't meet the lender's valuation expectations.
How to get the most accurate mortgage in principle
- Be honest and precise. Overstating income or understating debts only creates problems later when the full application doesn't match.
- Check your credit report first. Understanding what a lender will see means fewer surprises.
- Use a broker for a "whole of market" view. A broker can compare which lenders are likely to offer you the most favourable terms before you commit to a search.
- Avoid new credit applications in the weeks around getting your mortgage in principle and full application, as new credit searches and accounts can affect your score.
Worth reading next: our guide on How Much Deposit Do You Really Need for a UK Mortgage?, and Mortgage Affordability: How Lenders Really Decide.
To run your own numbers, try our Mortgage Affordability Calculator.
The bottom line
A mortgage in principle is a useful, low-risk first step that shows sellers you're a credible buyer and gives you a realistic budget before you start viewing properties. It isn't a promise of lending, so keep house-hunting grounded in reality, protect your credit file by checking whether searches are soft or hard, and be ready for a more thorough check once you make a formal application.