Buy-to-Let Calculator

Lenders do not always assess the rent using the interest rate you will actually pay. They may use a higher, notional rate to allow for the possibility that borrowing becomes more expensive in the future.

The test also seeks to leave a margin for the costs and risks of letting property, including maintenance, insurance, management fees, periods without a tenant and tax liabilities.

The difference can be considerable. Two lenders looking at the same property, receiving the same rent and offering similar headline interest rates may arrive at very different maximum loan amounts.

That is why a property can be perfectly serviceable in practice but fail a lender's stress test.

Yes, it can, and this is an important consideration before you purchase an investment property.

Property held in your personal name

Lenders commonly apply different ICR requirements depending on your tax position. A basic-rate taxpayer may be assessed at 125%, while a higher-rate or additional-rate taxpayer may face 140%, 145%, 160% or another threshold, depending on the lender and the property.

The tax treatment matters too. For individuals letting residential property, mortgage finance costs are generally no longer deducted in full when calculating taxable rental profits. Instead, relief is normally given through a basic-rate tax reduction, subject to the relevant rules and limits.

Property held through a limited company or SPV

Many limited company buy-to-let lenders apply a 125% ICR to standard single-let properties. This can sometimes allow the same rental income to support more borrowing than if a higher-rate taxpayer purchased the property personally.

A company may generally deduct qualifying mortgage interest when calculating its taxable property profits for Corporation Tax purposes. However, company ownership introduces other considerations: company running costs, mortgage pricing and fees, personal guarantees, and the tax consequences of withdrawing profits.

A limited company is not automatically the right choice. If you already own the property personally, transferring it into a company may give rise to Stamp Duty Land Tax or the equivalent devolved tax, Capital Gains Tax and other costs, depending on the circumstances.

We can explain the mortgage implications and work alongside your accountant or tax adviser so that the lending decision supports your wider plans, rather than determining them.

This is especially relevant for higher-value properties in London and the South East, although it is by no means limited to those areas.

A property may have considerable equity and a relatively low loan-to-value ratio, but still fail the lender's rental stress test because the rental yield is low.

The valuation tells us what the property may be worth. The ICR helps determine how much debt the rent can support. These are two separate constraints, and the lower of the two limits can determine the practical borrowing available.

Understanding this early can save time, unnecessary valuation fees and the frustration of pursuing a lender whose criteria were never suited to the property.

The basic ICR calculation is only the starting point for more complex investments.

If you have four or more mortgaged buy-to-let properties, lenders may treat you as a portfolio landlord and review the background portfolio as well as the new property. Existing mortgages, rental income, vacancies and the overall level of borrowing can affect the result.

Houses in multiple occupation (HMOs), multi-unit freehold blocks and holiday lets can also be assessed differently from a conventional single-let property. Some lenders apply higher coverage ratios or use different methods to establish the acceptable rental income.

These are areas where taking the time to find the right lender can make a real difference.

• What ICR do buy-to-let lenders use?

  125% is a common starting point for basic-rate taxpayers and standard limited company applications. Higher-rate personal applicants and specialist property types may face higher thresholds, sometimes materially higher. The applicable figure depends on the lender's current rules.

• How is the minimum rent calculated?

  Multiply the mortgage amount by the stress rate and the ICR, then divide by 12. For example, a £580,000 mortgage at 5% stress and 125% ICR requires slightly more than £3,020.83 per month, so £3,020.84 when rounded up to the next penny.

• Will a limited company always allow me to borrow more?

  No. It may give a more favourable ICR with certain lenders, but the result also depends on the stress rate, product, property, fees, loan-to-value limit and the lender's company criteria. Ownership should not be chosen on mortgage affordability alone.

• Is the mortgage stress rate the interest rate I actually pay?

  Not necessarily. It is the rate used to test affordability. The product rate, the stress rate and the lender's reversionary rate can all be different.

• Can a lender use my salary if the rent is too low?

  Some lenders offer top slicing, where suitable personal income may help meet an affordability shortfall. Eligibility and the method used vary by lender.

• Does a five-year fixed rate always improve affordability?

  No. It can make a substantial difference with lenders offering a more favourable five-year assessment, but others retain stress-rate floors or additional margins. The total mortgage cost also needs to be considered.

• Can I remortgage if the rent no longer meets today's stress test?

  Possibly. Like-for-like remortgages, especially where no additional borrowing is requested, can be assessed differently. It is worth checking the criteria before assuming you have to remain with the existing lender.