Mortgage in principle: what it is and when to get one

Almost every UK estate agent will ask for a mortgage in principle before they'll arrange a viewing on a desirable property. Most buyers get one, hand it over, and move on. But a mortgage in principle is much more limited than it sounds — and getting one at the wrong time, or with the wrong lender, can hurt your final mortgage application. This guide covers what it actually means, when to get one, and what to watch for.

What a mortgage in principle actually is

A mortgage in principle (MIP), also called an agreement in principle (AIP) or decision in principle (DIP), is a written statement from a lender saying they'd be willing to lend you a specified amount, subject to a full application and underwriting.

It's based on a short fact-find — your income, basic outgoings, deposit, the property type you're targeting — and a credit check. It is not a mortgage offer. The lender can still decline at the full application stage if anything material changes or surfaces during underwriting.

Soft vs hard credit search — and why it matters

Most reputable MIP applications use a soft credit search, which doesn't leave a visible footprint on your credit file for other lenders to see. Some lenders still use a hard search, which does — and multiple hard searches in a short window can drag your credit score down.

Before applying, ask explicitly: 'Is this a soft or hard search?' If it's a hard search, only apply once you're serious about that lender. Brokers usually arrange MIPs through soft-search-enabled lender portals.

How long it lasts

Most MIPs are valid for 60–90 days. After that, you'll need to refresh it. Lenders also refresh affordability calculations annually as criteria and rates change, so an old MIP can become unreliable even before it formally expires.

If you've been house-hunting for more than three months, renew your MIP before making any serious offer — your bargaining position weakens if a vendor calls your bluff and finds your evidence stale.

When to get one

Get an MIP after you've broadly settled on a price range, before you start putting offers in. Estate agents will increasingly insist on seeing one before they relay an offer to the vendor.

The two common mistakes: getting one too early (before you know your budget or before you've understood your monthly affordability), or getting one too late (after you've fallen for a property and feel pressured to rush).

Direct lender vs broker

A direct lender MIP gives you that one lender's view of what they'd lend. A broker, using affordability tools across the market, can give you a view of the best available across many lenders and find the one whose criteria fit you best.

For most first-time buyers, broker MIPs are worth the small time investment — your circumstances might be more affordable to one lender than another in ways you can't easily see from the outside.

What can still go wrong at full application

Even with an MIP in hand, the full application stage can throw up issues: undeclared debt or credit card balances, a valuation that comes in below the offer price, sustained employer status changes, or recent missed payments on any line of credit.

A "down-valuation" — where the lender's surveyor values the property below your offer price — is one of the most common reasons MIPs translate into a smaller-than-expected mortgage offer. How AVMs go wrong explains the mechanics.

Practical: improving your MIP outcome

Before applying: pay down any short-term credit (credit card balances, store cards), check your credit file for any errors, and avoid taking out any new credit lines for at least three months. Make sure you're on the electoral roll at your current address.

Have ready: three months' payslips, three months' bank statements, two years' P60s (or for self-employed, two to three years' SA302s and tax overviews), photo ID, and proof of address.

Frequently asked questions