Buying & Affordability
What is a mortgage in principle?
A mortgage in principle (MIP), sometimes called an Agreement in Principle or Decision in Principle, is a written statement from a lender saying how much they would in principle be willing to lend you, based on a soft credit check and the income and outgoings you declare. It is not a binding mortgage offer. MoneyHelper explains that an MIP usually lasts between 30 and 90 days.
Most estate agents will ask to see one before they pass an offer to the seller, because it shows the offer is realistic. The lender's full underwriting comes later: a hard credit search, payslips, bank statements, ID checks, and a property valuation. Any of those can change the figure or, occasionally, withdraw the offer altogether under FCA MCOB 11.6 responsible-lending rules.
Use an MIP to set a realistic price ceiling before you start booking viewings.
What this means in practice
A couple in BS3 with a joint income of £72,000 and a £35,000 deposit applies for an MIP through their broker. The lender runs a soft search, applies a 4.5x income multiple, and issues an MIP for £324,000 valid for 60 days. They view a £350,000 terrace, the agent asks to see the MIP before passing on their £340,000 offer, and the seller accepts. Two weeks later the full application uncovers a missed credit-card payment from 2024; the lender reduces the offer to £305,000. The buyers either find a £20,000 top-up or renegotiate. The MIP set the ceiling, but only the formal offer counts.
Related questions
Does a mortgage in principle affect my credit score?
Most lenders run a soft search at the MIP stage, which leaves no visible footprint on your credit file and does not affect your score. A handful still run a hard search — always ask before you submit. The full mortgage application later is always a hard search, and several full applications inside a short window can dent your score. Stick to one MIP at a time, and only convert to a full application once you have an offer accepted on a specific property.
How long does a mortgage in principle last?
Typically 30, 60 or 90 days depending on the lender. If you have not had an offer accepted before it expires, you can usually renew it with a fresh soft search. Renewing is sensible if your circumstances have not changed; if your income, debts or deposit have shifted materially, redo the affordability calculation first. The Permanent Mortgage Guarantee Scheme from July 2025 lets some lenders offer 95% LTV products, which may change the maximum on renewal.
Sources
Building with UK property data?
Homedata returns 29 million UK properties — UPRN, EPC, Land Registry, risk — keyed by a single ID. Free tier, no card.
Get a free API key