An Agreement in Principle (AIP) — sometimes called a Decision in Principle (DIP) or Mortgage Promise — is a lender's indicative confirmation that they would lend you a specific amount based on a soft credit check and basic income details. It's not a binding mortgage offer, but it tells estate agents and sellers you're a serious, proceedable buyer. Most first-time buyers should get one before serious property viewings.

What an AIP is — and isn't

An AIP is:

• A statement from a lender that they'd lend up to a specific amount.
• Based on soft credit search + your declared income, debt, and deposit.
• Valid for 30-90 days typically.
• Free to obtain (sometimes called "mortgage promise").

An AIP isn't:

• A guaranteed mortgage offer — the lender can still decline at full application.
• A commitment to that specific rate or product.
• A reservation of funds.
• Property-specific (you don't need to have a target property).

Why you need one

Three practical benefits:

1. Estate agents take you seriously. Most won't book viewings or accept offers without confirmation of buyer status. The AIP is that confirmation.
2. Sellers prefer your offer. Two offers at the same price — one backed by an AIP, one not — the AIP-backed offer usually wins.
3. You know what you can afford. Before viewing homes you can't borrow on, the AIP gives you a realistic budget.

Soft vs hard credit checks

The critical distinction in 2026 mortgage applications:

Soft credit check

Records on your credit file but not visible to other lenders. Doesn't affect your credit score. Most modern AIPs use soft checks. Common AIP providers using soft: Halifax, NatWest, Nationwide, Santander, HSBC (now), Barclays, Coventry, Skipton.

Hard credit check

Visible to all lenders and credit reference agencies. Multiple hard checks in a short window (6-12 months) can hurt your credit score. Some smaller lenders and specialist lenders still use hard checks for AIP.

Best practice: confirm the lender uses soft search before submitting AIP. If you need to compare multiple lenders, restrict to soft-search AIPs only. Hard searches at full application are unavoidable but accepted once you've chosen a lender.

How to get an AIP

Through a mortgage broker

A whole-of-market broker assesses your circumstances and identifies the lender most likely to approve at the best terms. Often the fastest route. Brokers charge £300-£600 fee or take lender commission.

Direct with a lender

Apply online via the lender's website. Most major UK lenders have AIP processes that take 15-30 minutes online with instant decisions. Quick if you know which lender suits you.

What you need ready

• Income details (gross annual)
• Bonus, commission, or variable income (averaged)
• Employment details (employer, length of service)
• Self-employed: 2-3 years' net profit / SA302 figures
• Deposit amount and source
• Existing debts (credit cards, loans, car finance, student loans)
• Monthly outgoings (utilities, transport, food, childcare, etc)
• Address history for the last 3 years
• Date of birth, national insurance number

What lenders check at AIP

The lender's AIP decision is based on:

• Affordability: Income vs ongoing commitments. Maximum borrowing typically 4-5× annual income (sometimes 5.5-6× for high earners or low LTV).
• Stress test: Could you afford payments if interest rates rose to 7-8%? See the stress test guide.
• Credit file: Soft search reveals any defaults, CCJs, or bankruptcies. Recent missed payments are red flags.
• LTV: Your deposit vs property value. Most lenders cap at 95% LTV for FTB.
• Employment status: Permanent employees easiest. Self-employed need 2-3 years' track record. Probationary period or contract roles often need 6+ months in role.
• Age vs term: Most lenders won't lend past age 70-75. So a 50-year-old applying for 30-year mortgage may be capped at 25 years.

Validity period

AIPs typically last:

• 30 days (some smaller lenders)
• 60 days (common)
• 90 days (Halifax, NatWest, some others)

If your property search drags on, refresh the AIP. The refresh is usually a quick process if your circumstances haven't changed. Don't let it expire mid-purchase — having no AIP at the offer stage looks bad to sellers.

What lenders don't check at AIP

To understand the risk of AIP-to-offer failure, know what's not yet verified:

• Bank statements. Lenders haven't yet seen your spending pattern.
• Payslips and P60. Income is self-declared.
• Employer confirmation. Lenders don't contact employers at AIP.
• Hard credit check. A more thorough check happens at full application.
• Property. No valuation; no survey; no title check.
• SA302 / tax returns. Self-employed income not yet verified.

Any of these can derail the application between AIP and offer. That's why an AIP is indicative, not guaranteed.

Common AIP mistakes

Multiple hard-search AIPs

Applying to 5 lenders with hard searches in a short period can lower your credit score by 20-50 points. Use a broker or restrict to soft-search lenders only.

Misdeclaring income

Lenders take a careful view of variable income — bonus and commission averaged over 2-3 years. Don't include one-off bonuses as recurring. Don't undeclare debt — lenders see it via the credit check.

Letting the AIP expire mid-purchase

An expired AIP looks bad to sellers and conveyancers. Refresh proactively at the 60-75% point of validity.

Treating AIP as the offer

Some buyers assume the AIP means the mortgage is "in the bag" and miss the full application diligence. Stay tidy with bank statements and credit file between AIP and offer.

Changing jobs after AIP

Many lenders won't progress to offer if you change jobs after AIP. If a job change is imminent, time your AIP and full application around it.

Getting an AIP from one lender, applying to another

The AIP is lender-specific. If you switch lenders for the full application, you'll go through the full process again from scratch.

What happens after AIP

1. Property search. Use the AIP figure as your maximum budget.
2. Offer accepted. Notify your broker / lender same day.
3. Full mortgage application. Submit within days of offer acceptance. Provide all the documentation the lender requested.
4. Hard credit search. Now the lender runs the full check.
5. Income verification. Payslips, P60, bank statements, employer letter.
6. Property valuation. Lender's surveyor visits or does desktop valuation.
7. Underwriting. Lender's underwriter reviews the full file.
8. Mortgage offer issued. Typically 2-4 weeks after full application.

AIP and your wider preparation

Things to do before AIP application that improve your chances:

• Register on the electoral roll.
• Check your credit file at all three agencies.
• Settle any outstanding defaults.
• Reduce credit card balances below 30% of limit.
• Avoid new credit applications in the 3 months before AIP.
• Build savings track record — 3-6 months of bank statements that look stable.
• Avoid gambling transactions and overdraft use.

See the credit score guide for full credit prep and the mortgage decline guide for common rejection reasons.

Maximum borrowing — what the AIP figure means

The AIP usually shows a single number: the maximum the lender would advance. Calculated from:

• Income × multiple (typically 4-5×, sometimes 5.5-6×).
• Less existing debt commitments.
• Less other monthly outgoings.
• Subject to stress test at higher rate.

So a couple earning £80,000 combined with no debt might get an AIP for £360,000-£440,000. Add their deposit to see total property budget. Use the affordability calculator to model your own borrowing capacity.

AIP for self-employed buyers

Self-employed applicants face stricter requirements. Lenders typically want:

• 2-3 years of accounts or SA302/tax computations.
• Net profit (sole trader) or salary + dividends (limited company).
• Recent year's accounts may be required certified by accountant.
• Some lenders accept 1 year's accounts with broker support.

Self-employed AIPs take longer to process and are sometimes conditional on full document review. Engage a specialist broker for self-employed mortgages.

When you should get a second AIP

Some buyers benefit from getting AIPs from two different lenders during the property search phase. Scenarios:

• Comparing maximum borrowing: Different lenders apply different income multiples, so AIP figures can vary materially.
• Backup for non-standard property: Some lenders refuse certain property types (timber-frame, ex-LA flats); having a fallback AIP from a lender that accepts gives confidence.
• Self-employed buyers: Compare 1-year vs 2-year accounts treatment.

Always confirm both AIPs use soft credit checks. Two soft checks cause no credit harm.

AIP vs Decision in Principle vs Mortgage Promise

These terms are largely interchangeable in the UK market:

• Agreement in Principle (AIP): Most common UK term in 2026.
• Decision in Principle (DIP): Older terminology, still used by some lenders.
• Mortgage Promise: Marketing term used by a few high-street lenders.
• Mortgage in Principle: Some platforms use this.

All refer to the same product: an indicative pre-application confirmation from a lender that they'd lend a specified amount subject to full underwriting.

Frequently asked questions

What is an agreement in principle?

A lender's indicative confirmation of how much they'd be willing to lend based on a soft credit check and basic income details. Not a binding mortgage offer but tells estate agents you're a serious, proceedable buyer.

Is an AIP a hard or soft credit check?

Most modern AIPs use a soft credit check. A handful of lenders still use hard checks for AIP — avoid these where possible. Multiple hard checks can lower your credit score.

How long does an AIP last?

Typically 30-90 days, varying by lender. Most are 60 or 90 days. If your search drags on, you can refresh by submitting an updated application.

What do lenders check for an AIP?

Basic identity, income, employment, deposit source, debts, monthly outgoings, and a soft credit check. Income is self-declared at this stage.

Do I need an AIP before viewing properties?

Not legally, but practically yes for any serious buyer. Many estate agents won't book viewings without confirmation of buyer status. Sellers prefer offers backed by an AIP.

What's the difference between AIP and mortgage offer?

AIP is indicative — based on basic info and soft check. Mortgage offer is the formal commitment — issued after full underwriting including income verification, hard check, and property valuation.

Can my AIP be turned down at full application?

Yes — an AIP isn't a guarantee. Common reasons for AIP-to-offer failure: undisclosed debt, gambling on bank statements, employment change, or property valuation issues.

What if I'm declined for an AIP?

Don't immediately apply to other lenders. Speak to a mortgage broker who can assess why and steer you to a lender likely to accept.

What an AIP doesn't lock in

An AIP isn't a rate lock or product reservation. Rates can move between AIP and full application, and the AIP figure becomes stale if your circumstances change. Specifically, the AIP doesn't reserve a specific mortgage product or rate, and the lender may change their LTV/rate matrix between AIP and full application. Plan to proceed quickly once you've had an offer accepted.

Related guides

Related calculators

Last reviewed: 6 June 2026.