PropCalc UK

The flagship UK buy-to-let calculator: a full month-by-month, after-tax cash-flow projection over a 25-year horizon, with Section 24 applied per year (or corporation tax for SPVs), mortgage amortisation handling the fix-then-revert rate transition, and CGT computed at every possible sale year so you can see your peak annualised total return. Capital appreciation, rent growth and cost inflation are all configurable. The 2pp property-income rate change from April 2027 is applied automatically from projection year 2 onward.

May 2026 • 2026/27 tax yearMoat · the full model

Full BTL Investment Model

The flagship rental model — projects a full horizon under the chosen ownership structure, computes equity build and CGT at every year, and finds your optimal exit year.

From 6 April 2027 — separate property income tax rates (22% / 42% / 47%)

Autumn Budget 2025 introduced a +2pp surcharge on rental income above the equivalent earned-income rates. The Section 24 reducer also steps up from 20% → 22%. This calculator applies the new rates automatically from year 2 onwards in any multi-year projection.

EPC C minimum from 1 October 2030 (new and existing tenancies)

£10,000 capex cap per property (down from proposed £15k), reviewed every 5 years. A new 4-metric EPC methodology goes live October 2026 — fossil-fuel heating may make a C-rating impossible without a heating swap (£8k–£15k of its own). For F/G/D-rated stock this can move hold-vs-sell. Add to your refurb capex line if your property isn't already C-rated.

High Value Council Tax Surcharge — from April 2028 (properties >£2m, England only)

Annual charge payable by the owner: £2,500 (£2m–£2.5m) · £3,500 (£2.5m–£3.5m) · £5,000 (£3.5m–£5m) · £7,500 (>£5m). 5-yearly revaluations. Material annual cost for prime London BTL — not yet modelled in cash-flow projections; add manually to operating costs from year 3 onwards if your property crosses the £2m threshold.

IHT exposure — BTL does NOT qualify for Business Property Relief

Buy-to-let property is fully exposed to 40% IHT above the frozen £325k NRB (+ £175k RNRB if applicable, tapered above £2m estate). Both nil-rate bands frozen to April 2031. For a £1m portfolio with no other estate planning, you're looking at ~£200–£270k of IHT exposure. Not modelled in cash-flow projections; worth a separate planning conversation with an STEP-qualified adviser.

My scenarios (0/10)

Save snapshots of your inputs to switch between scenarios (e.g. “65% LTV, higher-rate” vs “75% LTV, basic-rate”). Stored in your browser only — no login needed.

Acquisition & optimal exit

All-in cash

£84,000

SDLT

£15,000

Loan

£187,500

Optimal sale year

Year 25

Annualised return by exit year

The 'when to sell' answer — the year peak annualised return is achieved.

Equity build

Mortgage paydown + appreciation = your equity over time.

Annual after-tax cash flow

Use these together

Calculators that pair naturally with this one.

CGT + Optimal Sale Year

Drill into the exit decision

Section 24 Multi-Year

See the tax engine standalone

Rental Comparison

Run this deal vs other deals

Related guides

Plain-English explainers for the rules behind this calculator.

When to Sell a BTL: The Optimal Exit-Year Method

12 min read

Frequently asked questions

Answers to the questions UK property investors most often have about this tool and the underlying rules.

How does the optimal-exit-year work?
For every year of the hold horizon, the calculator computes: (i) cumulative after-tax cash flow received so far, (ii) net sale proceeds after estate-agent fees and CGT (band-split using your current income), (iii) the resulting annualised return from acquisition. The "optimal" year is the one with the highest annualised return. Holding too long can drag the IRR down even with continuing rent growth, because each marginal year contributes less return than the average.
Does this calculator handle a 5-year fix?
Yes. Set "Fixed period (years)" to 5 and "Revert rate" to your expected SVR/product-transfer rate after the fix ends (typically 6-8% in 2026). The model uses the initial rate for the fixed period then re-amortises the remaining balance over the remaining term at the revert rate.
Is CGT correctly modelled?
Yes. Residential CGT in 2026/27 is 18% in the basic-rate band and 24% above (post-October 2024 rates). The £3,000 annual exempt amount is applied, and the gain is band-split against your other income (so the same property generates different CGT for a basic-rate vs higher-rate seller). PRR and Lettings Relief are not modelled in this calculator — use the dedicated CGT calculator for those edge cases.
What if I want to model rate rises?
Use the Rate Shock / Refinance Cliff calculator for an isolated rate-shock analysis. For multi-year integration, the BTL Model assumes the post-fix rate stays constant — set "Revert rate" to a realistic worst-case (e.g. 7-8%) to stress-test.