Buy to Let Mortgage Limited Company Calculator
Model borrowing, rental cover, mortgage costs, and post tax cash flow for a buy to let property purchased through a UK limited company. This calculator is designed for landlords who want a quick view of deal viability before speaking to a broker, lender, tax adviser, or solicitor.
Enter your investment assumptions
Total agreed purchase price in pounds.
Typical limited company buy to let deposits start around 20 to 25 percent.
Annual mortgage rate used for payment calculations.
Used to estimate maximum borrowing under rental cover rules.
Most buy to let products are interest only, but repayment can also be modelled.
Required for repayment calculations and long term planning.
Use realistic market rent, not best case rent.
Insurance, maintenance, management, void allowance, and admin.
Use the rate relevant to your company profits and adviser guidance.
Rental coverage ratio often applied by buy to let lenders.
Add arrangement, broker, legal, and valuation fees if known.
For company setup, conveyancing extras, refurb, or contingency.
Optional, useful if you want to compare one property against another.
Results
Ready to calculate.
Enter your figures and click the calculate button to see loan size, monthly mortgage cost, rental stress test, yield, and estimated company profit after corporation tax.
Expert guide to using a buy to let mortgage limited company calculator
A buy to let mortgage limited company calculator helps landlords estimate whether a property stacks up financially when the purchase is made through a company structure rather than in personal names. The headline figures most investors care about are simple: how much deposit is needed, how much the mortgage will cost each month, whether the rent meets lender stress testing, and what cash flow may remain after running costs and corporation tax. The detailed answer, however, is more nuanced. Limited company borrowing can create tax planning opportunities for some landlords, but it also introduces legal, accounting, lender, and operational considerations that need to be understood before an offer is accepted.
This page is designed to bridge that gap. The calculator gives you a practical first pass, and the guide below explains how experienced investors interpret the numbers. If you are comparing a personal buy to let mortgage with a limited company buy to let mortgage, your decision should not be driven by one figure alone. You need to look at funding, tax, rental cover, portfolio strategy, and the longer term exit plan.
What this calculator measures
The calculator above focuses on a core set of buy to let company metrics that matter at underwriting stage and cash flow stage:
- Loan amount, based on purchase price and deposit percentage.
- Loan to value, often abbreviated to LTV, which lenders use to price risk.
- Monthly mortgage payment, using either interest only or repayment assumptions.
- Annual rental income and annual operating costs, to show the property level profit before financing.
- Interest coverage ratio, also known as ICR, which is one of the most important buy to let lending tests.
- Estimated maximum loan by stress test, based on rent, stress rate, and lender rental cover requirement.
- Estimated profit before and after corporation tax, which helps with initial viability checks.
No online calculator can replace bespoke tax advice, but a good one quickly reveals whether a deal is obviously workable, borderline, or unlikely to satisfy lending criteria.
Why limited company buy to let mortgages are different
When a property is owned by a limited company, the borrowing is usually made to a special purpose vehicle, often called an SPV. Lenders underwrite the property and the directors behind the company. They will usually review credit profile, landlord experience, rental income assumptions, deposit level, and the legal structure of the company. Unlike a standard residential mortgage, the focus is not your salary alone. The property must usually support itself. That is why the rental stress test is central.
For many higher rate taxpayers, limited company ownership became more popular after changes to mortgage interest tax relief for personally held buy to let property. In a company, mortgage interest is generally treated as a business expense for corporation tax purposes, subject to prevailing tax law and the company’s circumstances. That does not mean a company is always better. If you intend to draw profits immediately, there may be a second layer of personal tax when funds are taken out through salary, dividends, or other routes. A calculator can show company level profitability, but your adviser should model the full extraction strategy too.
How to read the key outputs
1. Deposit and loan size. A lower deposit increases leverage, but it also raises the mortgage balance and can reduce monthly cash flow. Many buy to let limited company products sit around 75 percent LTV, although some lenders go above or below this depending on property type and borrower profile. If your desired loan exceeds what the rent can support under the stress test, your practical borrowing limit may be lower than the LTV headline suggests.
2. Interest only versus repayment. Most landlords choose interest only because it reduces monthly commitments and can improve cash flow. Repayment borrowing amortises the loan, so monthly payments are higher, but debt reduces over time. The right choice depends on your income strategy, refinancing plan, and tolerance for future interest rate risk.
3. ICR and stress rates. This is where many first time investors get caught out. A property might look profitable at the pay rate but still fail affordability if the lender tests the loan at a higher stress rate and requires rent to cover that stressed payment by 125 percent, 140 percent, or 145 percent. The calculator therefore shows both current cost and stress test capacity.
4. Post tax profit. This is useful, but it should be treated as a screening figure, not a final tax calculation. Real company accounts can include finance costs, accountancy fees, capital allowances where relevant, repairs timing, director loans, and different tax treatment depending on facts and advice.
Typical decision process for investors
- Estimate realistic market rent, based on local comparables rather than optimistic listings.
- Choose a conservative mortgage rate and a separate lender stress rate.
- Enter full monthly operating costs, including management, maintenance, buildings insurance, compliance, and voids.
- Check whether the expected rent covers the lender ICR threshold.
- Review annual cash flow before and after corporation tax.
- Allow for fees and acquisition costs, including the higher rate stamp duty rules where relevant.
- Take the output to a mortgage broker and tax adviser for product selection and structure confirmation.
Comparison table: UK corporation tax rates relevant to limited company landlords
| Profit band | Corporation tax rate | Why it matters for landlords |
|---|---|---|
| Up to £50,000 | 19% | Smaller property companies may fall into the small profits rate, although associated company rules can affect the thresholds. |
| Over £50,000 and under £250,000 | Between 19% and 25% | Marginal relief can apply, so the effective rate can sit between the two headline rates. |
| £250,000 and above | 25% | Larger or more profitable property companies may face the main rate, which should be reflected in forecast cash flow. |
Source basis: HM Revenue & Customs corporation tax guidance. Always confirm current rates and associated company rules before relying on a projection.
Comparison table: Stamp Duty Land Tax rates for additional residential properties in England
| Standard residential band | Additional property surcharge applied on top | Investor relevance |
|---|---|---|
| Each main residential SDLT band | Higher rates for additional dwellings apply | Most buy to let acquisitions attract the additional dwelling surcharge, which materially changes total cash required. |
| Company purchases of residential property | Usually treated as additional property purchases | Limited company buyers often need to budget more cash upfront than owner occupiers. |
| Linked or unusual transactions | Special rules may apply | Complex purchases should be checked by a conveyancer or tax specialist before exchange. |
What a strong buy to let limited company deal often looks like
Experienced landlords rarely rely on a single metric such as yield alone. A stronger deal usually has several positive traits at the same time: rent that comfortably exceeds the stress tested mortgage payment, a realistic maintenance allowance, a reserve for voids, and enough margin left over to cope with rate changes. In many cases, the best deals are not those with the absolute highest gross yield, but those with the most resilient net cash flow after all costs are included.
- Healthy rent to loan relationship under a conservative ICR.
- Purchase price supported by local rental evidence and demand.
- No hidden major works or compliance issues that could drain cash reserves.
- Competitive limited company mortgage product with manageable fees.
- Clear plan for profit retention, refinancing, or eventual sale.
Common mistakes when using a buy to let company calculator
One frequent mistake is using the headline mortgage pay rate as the only affordability measure. Lenders often apply a separate stress rate and a required ICR, so a property that seems fine at 5.49% may not pass a stress test at 7.5% and 145%. Another mistake is underestimating operating costs. Even a well run property will need periodic repairs, compliance checks, and some allowance for voids or tenant turnover.
A third mistake is ignoring acquisition friction. Company setup costs, broker fees, valuation fees, solicitor costs, and higher rate stamp duty can significantly increase cash needed on day one. If the true all in cash requirement is underestimated, returns can look artificially attractive. The calculator above includes fee fields to help counter this issue, but you should still maintain a contingency buffer.
How lenders usually assess limited company buy to let applications
Most lenders look at the company structure, the property, and the people behind the company. If the company is an SPV with suitable SIC codes and clean ownership, the process can be more straightforward than if the company carries other trading activity. Personal guarantees are common. Credit history, age, property type, lease details for flats, EPC position, and portfolio exposure can all influence the available products. Portfolio landlords may face more detailed underwriting, especially where aggregate borrowing and background liabilities are substantial.
Remember that the maximum theoretical loan shown by a calculator is not always the same as the loan a lender will offer. Product fees, minimum income policies, portfolio rules, and property specific restrictions can change the final answer.
Should you buy in personal name or through a company?
There is no universal answer. For some investors, especially those planning to retain profits for future purchases, a company can be attractive. For others, especially where borrowing costs are higher in a company or where profits need to be extracted regularly, personal ownership may still deserve consideration. This is why an expert process normally combines mortgage advice with tax advice. The right structure depends on your wider income, number of properties, long term plans, and succession objectives.
Real world assumptions that improve forecasting accuracy
If you want more reliable results, work with conservative assumptions. Instead of using the highest advertised rent, check completed and currently let comparables nearby. Build in a realistic maintenance reserve, even for newer property. Add at least a modest void allowance. Model a slightly higher mortgage rate than today if you are trying to test resilience. On stronger deals, the numbers will still work even when conditions are a little tougher than expected.
It can also help to run multiple scenarios. For example, calculate one case at your expected rent, another at rent minus 5%, and a third at a higher mortgage rate. Investors who use scenario analysis generally make calmer decisions because they understand both the upside and the downside before they commit capital.
Authoritative resources you should review
- HM Government, corporation tax rates
- HM Government, Stamp Duty Land Tax residential property rates
- Office for National Statistics, private rental price data
Final thoughts
A buy to let mortgage limited company calculator is most valuable when it is used as a decision support tool rather than a promise. It helps you test viability, compare scenarios, and identify whether the proposed rent is strong enough to support the desired borrowing. It also gives you a more disciplined view of costs, which is essential in a market where rates, regulation, and operating expenses can all shift.
If your scenario produces healthy rental cover, a sensible LTV, and solid post tax cash flow, the next step is to verify the deal with a whole of market broker and a qualified tax adviser. If the scenario looks tight, that is useful too. It may mean you need a larger deposit, a cheaper property, a stronger rental area, lower fees, or a different ownership structure. Better to discover that before exchange than after completion.
Use the calculator regularly, keep your assumptions evidence based, and always cross check the final numbers against lender criteria and professional advice. That approach gives you the best chance of building a profitable, scalable, and resilient property portfolio through a limited company.