What a Mortgage in Principle Actually Is
A mortgage in principle is a conditional statement from a lender — not a binding offer. The lender reviews your income, outgoings, credit history, and deposit, and gives you a certificate confirming they would, in principle, lend you up to a stated amount. It typically takes 15–30 minutes to obtain online or over the phone.
It is not a mortgage offer. It does not guarantee your application will be approved when you submit it in full. Lenders can and do decline full applications even after issuing an AIP, if the property valuation comes in low, if your circumstances have changed, or if the full application reveals issues the initial check didn't catch.
Soft vs Hard Credit Checks
This distinction matters more than most buyers realise. A soft credit check leaves no visible mark on your credit file — other lenders cannot see it, and it does not affect your credit score. A hard credit check is recorded on your credit file and is visible to other lenders for 12 months. Multiple hard searches in a short period can reduce your credit score and signal financial stress to future lenders.
Some lenders run a soft check for the initial AIP and a hard check only on the full mortgage application. Others run a hard check at the AIP stage. Always ask specifically which type of check will be run before you proceed.
How to Get a Mortgage in Principle
You can apply directly through a lender's website or via a mortgage broker. Going direct is faster for a single lender's AIP but limits your market visibility. A mortgage broker can access products from multiple lenders, often including exclusive deals not available direct, and can advise on which lenders are most likely to accept your profile.
Most brokers charge a fee (typically £300–£500) or take a commission from the lender. Whole-of-market brokers compare the broadest range of products. If you're self-employed, have a non-standard income, or have had credit issues, a broker is particularly valuable — they know which lenders are accommodating for different profiles.
- ▸Direct with a lender: Faster for a single AIP, but you're limited to that lender's products and rates
- ▸Mortgage broker: Better market access, single credit search, expert advice on which lenders suit your profile
- ▸Comparison sites: Useful for initial research on rates, but AIPs from comparison sites still go through individual lenders
- ▸What you'll need: Proof of income (last 3 payslips or 2–3 years' accounts if self-employed), proof of deposit, details of outgoings and existing credit commitments
How Long Does a Mortgage in Principle Last?
Most AIPs are valid for 60–90 days. If you haven't had an offer accepted within that window, you'll need to renew it — which means another credit check. If your circumstances haven't changed, renewal is straightforward.
If your financial situation changes significantly between your AIP and your full application — a new credit card, a new car loan, a change in employment — inform your lender or broker immediately. Undisclosed changes that come to light during the full application can cause significant delays or a declined mortgage.
What Happens After the AIP
Once your offer on a property is accepted, you move from AIP to full mortgage application. This involves submitting verified documents — payslips, bank statements, proof of deposit source — and the lender will instruct a surveyor to value the property.
If the lender's valuation comes in below the purchase price (a 'down valuation'), they'll only lend against the lower figure. This means either finding additional deposit to cover the gap, renegotiating the purchase price down, or switching to a lender who values it differently. Down valuations are uncommon but do happen, particularly on properties that have been priced aggressively.
- ▸Full application timeline: Typically 2–6 weeks from full application to formal mortgage offer, depending on lender and complexity
- ▸Down valuation: If the lender values the property below your offer price, you have limited options — renegotiate, increase deposit, or switch lender
- ▸Mortgage offer validity: Formal mortgage offers are typically valid for 3–6 months — enough time to complete a standard conveyancing process
- ▸Exchange of contracts: You are not legally committed to the purchase until exchange — the mortgage offer confirms funding, not legal completion
Key Takeaways
- ✓An AIP/MIP/DIP is a conditional indication — not a binding mortgage offer — but essential for making competitive offers
- ✓Always ask whether the lender runs a soft or hard credit check at the AIP stage — multiple hard searches damage your credit score
- ✓Use a mortgage broker if you're self-employed, have complex income, or want access to the widest range of products
- ✓Do not take on new credit between your AIP and mortgage completion — it can derail your full application
- ✓If the lender's surveyor down-values the property, you have limited options: renegotiate the price, increase your deposit, or switch lender