Mortgage in Principle: How Long It Lasts and How Much It Really Proves
Updated 25 August 2026
A mortgage in principle tells an estate agent that you can probably borrow, not that you will. It is a lender's early screen on the figures you type in, and it expires. This guide sets out how long each major lender's agreement lasts, whether it touches your credit score, and why a case that passed in principle can still fail at full application. Mortgage One is a whole of market mortgage adviser arranging agreements in principle for buyers who want a figure that survives full underwriting.
For a free initial consultation on which lender's agreement in principle suits your income and deposit, call 01202 155992 or contact Mortgage One.
What is a mortgage in principle and what does it actually check?
A mortgage in principle is a lender's written indication of how much it may lend you, produced from the income, outgoings, deposit and address history you enter plus a credit check on your file. It is not a mortgage offer. Lenders call the same document an agreement in principle or a decision in principle, and the three terms are interchangeable.
The screen is shallow by design. You self-declare income and commitments, the lender runs a credit-reference search against your file and its scorecard, and an automated affordability model returns a maximum figure. Nobody has seen a payslip, a bank statement or the property. That is why an agreement in principle from a five-minute web form and a fully underwritten offer can land on very different numbers.
The document still does two useful jobs. It gives you a budget to search with, and it satisfies estate agents, who increasingly ask to see one before booking a viewing or passing an offer to the seller. For a first-time buyer it is usually the first piece of paper in the whole chain, and the one the agent phones your broker to check.
How long does a mortgage in principle last at each lender?
A mortgage in principle typically lasts between 30 and 90 days. The period is set by each lender rather than by any industry rule, so two buyers with identical finances can hold agreements that expire two months apart. When yours lapses you rerun the check, which takes minutes if your figures and the lender's criteria have not moved.
NatWest: 30 days. The shortest validity among the major high street lenders, which matters if you obtain the agreement before you have found a property. A NatWest agreement issued at the start of a search will usually need refreshing before you make an offer.
Santander: 60 days. Santander returns an instant online decision, so refreshing an expired agreement is a same-day job rather than a delay to the offer.
HSBC: 60 to 90 days. HSBC describes the decision as subject to a full assessment and not a guarantee of a mortgage, which is the wording every lender applies in substance even where the page does not say it.
Nationwide: 90 days, and the decision can be used to submit a full application straight away. Nationwide's longer window suits buyers early in a search who want one document to carry through viewings to offer.
Barclays: 90 days, provided the details you gave about income, regular spending and debts have not changed. Barclays makes the condition explicit. Every lender applies it in practice: a new car finance agreement, a job change or a missed payment voids the agreement whatever the calendar says.
Broker-side, the expiry date is rarely the constraint. Rate changes, criteria changes and product withdrawals reset the picture more often than the 90 days do. A refreshed agreement in principle is usually free and takes minutes, so the practical rule is to rerun it on the day you find the property you want to bid on, with the lender you actually intend to use.
Does a mortgage in principle affect your credit score?
Most lenders run a soft credit search for a mortgage in principle, which is visible only to you and leaves your credit score untouched. Some still run a hard search that other lenders can see. Ask which before you apply, because a run of hard footprints before a full application is what an underwriter does not want to find.
Santander, for example, states that its online decision in principle is a soft search only and will not affect your credit score or your ability to borrow in future. The major lenders now broadly follow the same approach, but the position is lender-specific and changes, so it is worth confirming on the day rather than assuming.
The trap is not the single agreement. It is the buyer who runs one with five lenders in an afternoon to compare figures. If two of the five use hard searches, the credit file now shows two mortgage applications in a week and no completed mortgage, which an underwriter reads as declines. One agreement, with the lender you intend to use, is the right number. The mortgage credit check guide explains how soft and hard searches are recorded and how long they stay visible.
Before any lender searches you, download your credit report yourself. That is a soft search, it shows you what the lender's scorecard will see, and it surfaces the old address, the financial association or the forgotten catalogue account that would otherwise turn up at full application.
How reliable is a mortgage in principle once you apply in full?
A mortgage in principle is reliable on the narrow point it tests, that your declared figures pass the lender's scorecard, and unreliable on everything it has not yet seen. Full application adds verified payslips, bank statements, a hard credit search and a property valuation. Halifax's own wording is that the lender may change its decision or offer different terms.
In practice the figure moves for three reasons. First, income is keyed differently. A buyer types a salary that includes bonus and overtime. The underwriter takes basic pay in full and the variable elements at a reduced percentage averaged over previous years, and the maximum loan drops. Second, commitments surface that were left off the form: car finance, buy-now-pay-later balances, childcare, a student loan deduction on the payslip. Third, the property fails a criterion the agreement never asked about: a flat above a takeaway, a short lease, a new build above the lender's loan-to-value cap, or a non-standard construction type the lender will not take.
The gap between the two figures is the same gap that opens between an online calculator and a real lending decision, and the mortgage affordability guide sets out how the deductions and stress test work. The income multiples a lender applies are only the starting point.
A broker-run agreement in principle closes most of that gap. Mortgage One keys the case through the lender's intermediary portal with income broken down the way its underwriter will treat it, commitments taken from your credit file rather than from memory, and the property type checked against criteria before the search is run. The number that comes back is the number the offer is likely to carry.
Why a mortgage in principle can still be declined at full application
Declines after an agreement in principle almost always trace to something the agreement never examined: verified income lower than the figure declared, undisclosed credit commitments, bank statement conduct, a property that fails lender criteria, or a change in circumstances between the two stages. Experian notes that lenders reconsider when a financial situation has changed or the property raises specific issues.
The cases Mortgage One sees declined after an agreement in principle fall into a short list. A commitment left off the form, most often car finance or a personal loan taken out between the agreement and the application. Bank statements showing gambling transactions, returned direct debits or a persistently used overdraft. A job change that puts the applicant inside a probation period. A deposit that cannot be evidenced back to source, which the mortgage deposit guide covers in detail. Adverse entries that the soft search's headline score did not surface but the full search does. And a valuation that comes in below the agreed price, moving the loan into a loan-to-value band the lender does not offer at that income.
A decline at this stage is a decline from one lender's criteria on one set of facts, not a decline from the market. The next step is to read the reason, fix what can be fixed, and place the case with a lender whose criteria fit, rather than reapplying to the same lender or firing applications at three more. The declined applications guide sets out the sequence, and where the reason is credit history the bad credit mortgage guide covers which lenders look past it.
If your income includes bonus, overtime, contract or self-employed earnings and you want an agreement in principle placed with a lender that will still say yes at underwriting, call 01202 155992 or contact Mortgage One.
How to get a mortgage in principle that estate agents will accept
To get a mortgage in principle you enter your personal details, three years of address history, income, outgoings and deposit on a lender's website or through a broker, and a credit check runs against them. Halifax puts its online form at around ten minutes with no impact on your credit score. Estate agents accept the certificate as proof of borrowing.
The information every lender asks for:
• Your full name and date of birth
• Your address history going back three years
• Your income, and how it is made up
• Your monthly expenses and credit commitments
• The size of your deposit
Direct with a lender, you get that lender's view of your case. Through a whole of market mortgage broker, you get the agreement from the lender most likely to underwrite the case, which is the difference that matters for the self-employed, for contractors, for buyers paid in a foreign currency and for anyone with a blemish on their credit file. A high street web form has no field for retained profit, day rates or Seafarers Earnings Deduction income. The lender's intermediary portal does.
Ask for the certificate as a PDF showing the lender's name, your name, the maximum loan, the date of issue and the expiry. Agents see these every week and some will phone the broker named on it to confirm. The agreement proves borrowing. It does not prove the deposit, so expect the agent to ask for a bank statement or a solicitor's letter for that as well.
From mortgage in principle to mortgage offer: what happens next
After the agreement in principle comes the full application, where the lender verifies documents, runs a hard credit search, instructs a valuation and underwrites the case before issuing a mortgage offer. MoneyHelper puts the wait from application to offer at typically two to four weeks. The offer carries its own expiry, set by the lender, and can usually be extended.
The sequence that keeps a purchase moving is simple. Run the agreement in principle before viewings so the budget is real. Refresh it on the day you offer, with the lender the case will actually go to. Submit the full application within days of the offer being accepted, with payslips, bank statements and deposit evidence already assembled, so the valuation is booked while the seller is still warm. The mortgage application guide lists the documents lenders expect, and the mortgage approval guide covers what underwriters check first.
If you have not yet run an agreement in principle and want a realistic figure before you do, the how much can you borrow calculator shows the range lenders are likely to land in, and where the deductions that shrink it come from.
To have Mortgage One run a soft-search agreement in principle with the right lender before your next viewing, call 01202 155992 or contact Mortgage One.
The information provided in this article is for general guidance only and does not constitute personal or regulated financial advice. If you'd like to understand what these moves could mean for you, speak to Mortgage One. We can explain your options and timings based on your specific circumstances.
FAQs
1. Is there a downside to getting a mortgage in principle?
Only if the lender uses a hard search or you obtain several agreements in a short period. A single soft-search agreement has no effect on your credit file. The other downside is over-confidence: treating the figure as an offer and bidding on a property the full application cannot support.
2. Can I get a mortgage in principle without a credit check?
No. Every lender runs a credit check to produce an agreement in principle. What varies is the type. Most use a soft search that leaves no visible footprint, while some use a hard search that other lenders can see. A broker will tell you which applies before it is run.
3. Can you be declined after a mortgage in principle?
Yes. The agreement is not a commitment to lend. Verified documents, the full credit search, the valuation and any change in your circumstances can each change the lender's decision. Declines after an agreement in principle are almost always about facts the agreement never tested.
4. How long does a mortgage in principle take to get?
Online, most lenders return a decision immediately or within the hour once you have your income, outgoings and address history to hand. Experian puts the form at around 15 minutes with a maximum wait of 24 hours where a manual review is needed.
5. What do you need for a mortgage in principle?
Your full name and date of birth, three years of UK address history, gross income and how it is made up, monthly commitments such as loans, credit cards and childcare, and your deposit amount. Nationwide also asks for your National Insurance number.
6. What is the difference between a decision in principle and an agreement in principle?
Nothing. Decision in principle, agreement in principle and mortgage in principle describe the same document. Which name you see depends on which lender issued it, not on how strong it is or how long it lasts.
7. Should I get a mortgage in principle through a broker or direct from a lender?
Direct works when your income is straightforward salary, your deposit is saved, your credit file is clean and you already know which lender you want. Through Mortgage One, the agreement is placed with the lender chosen for your case, keyed the way that lender's underwriter will assess it, using a soft search wherever the lender offers one. For anyone with bonus, contract, self-employed or overseas income, that is the version an estate agent should be shown.