Guide · 9 min read
The SIC codes buy-to-let lenders accept (68100, 68209, 68320), the difference between them, what happens when the code is wrong, and how to fix it at Companies House.
Written by Matt Lenzie · Published 10 June 2026
Advice from
Matt Lenzie · 25+ year career banker (Bank of Scotland, Lloyds Banking Group). £300m+ raised for property clients.
25+ year career banker (Bank of Scotland, Lloyds Banking Group). £300m+ raised for property clients.
A SIC code is a five-digit Standard Industrial Classification code that tells Companies House, and everyone who reads the register, what a company does. For a buy-to-let company, the accepted codes are 68100, 68209 and, in a supporting role, 68320. Those four digits matter far more than most landlords expect, because mortgage lenders use them as the first and fastest test of whether a company is a clean special purpose vehicle.
We see the consequences from the broker side. A company registered years ago with a consultancy code, or a brand-new SPV filed in a hurry with the wrong division entirely, walks into a smaller, more expensive corner of the lender panel before the underwriter has read a single bank statement. This guide explains what each code means, how lenders actually use them, and how to fix a wrong one before it costs you a product.
Every UK company declares at least one SIC code on incorporation and confirms it annually on the confirmation statement. The codes come from a national classification scheme (the 2007 edition is current) that sorts all economic activity into numbered classes. Division 68 covers real estate.
The codes themselves are mundane: you pick up to four from a published list when you incorporate, and you confirm or amend them once a year. There is no approval process, no gatekeeper, and no charge for choosing well, which makes the SIC code the cheapest piece of underwriting equity a property company will ever hold.
Lenders care because limited company buy-to-let pricing is built on a premise: the borrower is a special purpose vehicle that does nothing except own property. No trading income to dry up, no business creditors competing for the company's cash, no unrelated risk sitting on the same balance sheet as the lender's security. The SIC code is the public, machine-readable declaration of that premise. When a lender's system pulls the Companies House record and sees 68209, the case proceeds as an SPV. When it sees a hairdressing or software code, the case either reroutes to a much smaller trading-company panel or stops.
It is worth being precise about what the code is not: it is not a licence, it does not bind the company legally, and HMRC does not tax you differently because of it. Its power is entirely about classification, and in company lending, classification is destiny.
The lender-friendly list is short:
The other division 68 code you will meet, 68310 (real estate agencies), describes an estate agency business and does not belong on a buy-to-let SPV. Most lenders criteria sheets name 68100 and 68209 explicitly; a company registered with both ticks effectively every box on the panel, from the specialist SPV lenders through to the intermediary-only building societies.
The two codes describe two different business models that often live in the same company.
68100 is a trading posture: property is bought to be sold, the way a retailer buys stock. A flipping or development-to-sell business is a 68100 business, and note that lenders view heavy flipping activity as trading risk even under a property code.
68209 is an investment posture: property is bought to be kept, and the income is rent. This is what a buy-to-let mortgage is underwritten against, and if your company will only ever hold one code, this is the one.
In practice we recommend registering both, and most accountants do the same, for a simple reason: portfolios change. The SPV that holds six flats today may sell two of them in five years, and having 68100 on the register from day one means that disposal sits comfortably inside the company's declared activity. No lender we place business with objects to the pair.
Strategy variants worth a sentence each. HMO and holiday-let operators sometimes ask whether the letting model changes the code: it does not, 68209 covers letting of own real estate whatever the tenancy type, and lenders assess the property strategy through criteria, not classification. Landlords running several special purpose vehicles, one per property or one per strategy, should register each with the same clean pair; consistency across the group reads well when a portfolio lender aggregates the exposure. And developers who build to sell are genuinely 68100-led businesses with different lending needs (development finance, not term buy to let), which is a structural conversation rather than a SIC one.
Three things, in escalating order of cost.
The panel shrinks. Lenders whose criteria require SPV-only borrowers fall away automatically. You lose access to a large slice of the market, including some of the sharpest pricing, before any human has assessed the case.
The pricing widens. The lenders that remain treat the company as a trading borrower. Trading-company buy-to-let exists, we arrange it, but it carries a rate premium and heavier underwriting: business accounts, sometimes debentures, more questions. You pay trading-company pricing for what is functionally an SPV, which is the worst trade available.
The case dies late. The most expensive version is the mismatch discovered at offer stage, when the lender's legal team reconciles the application against the register. A decline after weeks of valuation and conveyancing costs real money and sometimes the property itself. This failure mode features in our guide to why limited company mortgage applications get declined, because we see it repeatedly with companies set up years before the property plan existed.
A genuinely mixed company, one that trades and holds property, has a structural decision to make rather than a filing to fix: usually the cleanest route is a new SPV for the property, with the deposit moved by intercompany loan. Our SPV vs trading company guide weighs that choice.
Mercifully, this is the easy fix in company administration. SIC codes are updated through the confirmation statement, and you do not have to wait for the annual due date: you can file an early confirmation statement online at any time, the change shows on the public register within days. There is no separate fee beyond the statement's standard filing charge, currently £34 online.
Two practical notes from cases we have packaged. First, change the code before the mortgage application goes in, not during; underwriters notice same-week register changes and will ask about them, though a sensible explanation usually satisfies. Second, a code change does not erase history: if the company has actually traded, the accounts still show it, and the lender will underwrite the substance, not the label. The SIC code must match reality, not replace it.
No. HMRC determines tax treatment from what the company actually does, reported through its accounts and corporation tax return, not from the Companies House classification. A company with 68209 on the register pays corporation tax on its rental profits exactly as the numbers dictate; registering 68100 does not make HMRC treat your gains as trading profits, and vice versa. The distinction that does matter to HMRC, investment versus trading activity, is decided on the facts, which is a conversation for your accountant.
The SIC code's entire practical weight, for a landlord, sits on the lending side. That is also why getting it right costs nothing and getting it wrong costs basis points: the code is free, the SPV mortgage pricing it unlocks is not.
The two-minute checklist before any company applies for a limited company buy-to-let mortgage: 68100 and 68209 on the register, no stray codes, no trading activity in the accounts, deposit documented as a director's loan, and directors prepared for personal guarantees. Run your numbers through our buy-to-let stress test calculator to see what the rent supports at the 125% company ICR, then talk to us. If the company is not clean, tell us early: we place trading-company and mixed cases too, the routing just needs to be deliberate.
68100 is "buying and selling of own real estate": the company trades property as stock, buying to resell. 68209 is "letting and operating of own or leased real estate": the company holds property and collects rent. A buy-and-hold landlord is a 68209 business; a flipper is 68100. Most buy-to-let SPVs register both so the company can sell a property without stepping outside its registered activity, and lenders are comfortable with either or both.
47300 is "retail sale of automotive fuel in specialised stores", in other words a petrol station, and it has nothing to do with property. It appears in property searches mainly because landlords stumble across it when browsing the SIC list. If a code like 47300 sits on a company that wants a buy-to-let mortgage, lenders will read the company as a trading business, not a special purpose vehicle, and most will decline or reprice.
The property SIC codes sit in division 68: 68100 (buying and selling of own real estate), 68209 (letting and operating of own or leased real estate), 68320 (management of real estate on a fee or contract basis) and 68310 (real estate agencies). For a company that exists to hold rental property, 68209 is the core code, usually paired with 68100. The agency and management codes describe service businesses, not landlords.
68209. It describes exactly what a buy-to-let company does: letting and operating its own real estate. Registering 68100 alongside it is standard practice and keeps a future sale inside the company's stated activity. There is no advantage in adding further codes, and genuine disadvantage in adding non-property ones, because every code on the register is a statement to lenders about what the company might do.
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