Does It Stack? UK Property Deal Calculator — Complete Edition (2026/27)

Most property calculators ignore stamp duty surcharges, Section 24, lender stress tests and the Renters' Rights Act, so the cashflow they show isn't the cashflow you'll get.

Does It Stack? is built for UK investors. Enter a deal and see your cashflow after tax, whether a lender will fund it, and what the rule changes coming up will cost you. Nine calculators in one Excel file, for less than most deal analysers charge for one strategy.

What's inside

• Buy to Let: stamp duty, Section 24 or corporation tax, after-tax cashflow, lender stress test, EPC C 2030 check, 10-year equity.
• BRR (Buy, Refurbish, Refinance): bridging costs, refurb contingency, refinance sized by LTV and rent cover, money left in, and the most you can pay to leave nothing in.
• Flip: profit after trading-income or corporation tax, return on cash, annualised return.
• HMO: room-by-room rents with bills, licensing and Article 4 flags, stress test.
• Rent-to-Rent: set-up cash, payback in months, margin check.
• Holiday Let: nightly rate, occupancy, platform fees, cleaning per stay, break-even occupancy.
• New Build Development: land SDLT, CIL, Building Safety Levy, biodiversity net gain, month-by-month finance drawdown, sensitivities, maximum land price, and a PASS / FAIL check against nine lender criteria.
• Stamp Duty: every buyer type side by side.
• Quick-Start Guide (PDF): six pages, tab by tab.

Why it's different

• UK rules as at 19 October 2026, with every rate on one Assumptions tab and a Regulatory Log of sources.
• The April 2027 property income tax rise is already modelled.
• Formulas protected so you can't break them by accident; password included if you want to customise.
• Free updates for 12 months. When the rules change, your download link gives you the new version.

What you get: one Excel file (.xlsx) and a PDF guide. Best in Microsoft Excel on Windows, Mac or the web.

Licence: for your own property decisions. Please don't share or resell the file.

Important: the calculator gives estimates to help you appraise a deal. It is not tax, legal, mortgage or financial advice. Rules modelled are for England and Northern Ireland.