Buy-to-Let Calculator
Estimate your monthly cash flow, annual profit after tax and return on investment for an interest-only buy-to-let mortgage — including the Section 24 mortgage-interest tax restriction.
Estimate only. This is an indicative estimate, not financial or tax advice. Speak to a mortgage broker and an accountant before investing in a buy-to-let property.
Enter your buy-to-let details
Your monthly cash flow, annual profit and return on investment appear here as you type.
How buy-to-let cash flow and tax are calculated
Your deposit is a percentage of the property price; the rest is the mortgage loan, on which we calculate interest-only monthly payments at your chosen rate. Monthly cash flow is simply your rent minus that mortgage interest minus your running costs, divided by twelve — the cash that actually lands in your account each month, before tax. Your annual tax bill works differently: since April 2020, HMRC no longer lets landlords deduct mortgage interest from taxable rental profit. Instead, tax is calculated on rent minus running costs only, at your Income Tax band, and then a 20% tax credit is applied against that bill based on your mortgage interest (Section 24). At higher tax bands this credit is worth less than the relief you'd get from deducting interest outright, which is why heavily-mortgaged properties can show a healthy cash profit but a much smaller — or even negative — profit after tax. Return on investment (ROI) compares your annual net profit after tax to the actual cash you put in: your deposit plus purchase fees such as legal costs, survey and Stamp Duty.