A whole-portfolio view of your UK buy-to-let business: aggregate rental income, total operating costs, blended LTV across all properties, and (most usefully) an interest-rate shock simulator that runs the entire portfolio through +1, +2 and +3 percentage point shocks on every mortgage — showing exactly how many properties go cash-negative and what the after-tax cash impact is. Section 24 is computed on the aggregate income, not per property, so the numbers reflect what you actually owe HMRC at year-end.
Portfolio Aggregator & Stress Dashboard
Roll your whole portfolio into one view. Aggregate Section 24 across all properties, see blended LTV, and watch each property's cash flow under rate-shock scenarios.
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.
Portfolio headlines
Total value
£600,000
Total equity
£150,000
Blended LTV
75.0%
Annual after-tax cash
-£1,880
Interest-rate shock
+0/+1/+2/+3pp across the whole portfolio — how many properties go cash-negative?
Cash-negative property counts at each shock: 0pp → 0 · 1pp → 1 · 2pp → 3 · 3pp → 3
Per-property after-tax cash & LTV
Use these together
Calculators that pair naturally with this one.
Related guides
Plain-English explainers for the rules behind this calculator.
Frequently asked questions
Answers to the questions UK property investors most often have about this tool and the underlying rules.
- Why aggregate Section 24 instead of per property?
- HMRC treats your property business as a single business. Profits and losses from individual properties are pooled before Section 24 is applied. So the aggregate view is the only correct view for tax purposes — analysing each property in isolation can mislead.
- How do I prepare for a rate-shock cliff?
- Identify which mortgages have fixed-rate periods ending soon (use the Rate Shock calculator for individual deals). For the portfolio, raise rents pre-cliff where possible, prepare to refinance via product transfer with the same lender (faster, no full re-underwrite), and have reserves in place for the cash-negative quarters in between deals.