A cheap-looking leasehold flat can carry expensive baggage: service charges that compound faster than rent, ground rent with doubling or RPI clauses, and a lease term that quietly slides toward the points where mortgages and buyers dry up. This calculator projects the full carrying cost over your planned hold and grades saleability against the three thresholds that matter — the 80-year mark where marriage value makes extension dramatically dearer, the ~70-year floor most lenders insist on, and the "onerous ground rent" tests that make a flat hard to mortgage at all. It is a screening tool, not a formal lease valuation.
Leasehold Risk Calculator
Project service charge and ground rent growth across your hold, and grade saleability against the 80-year marriage-value cliff, the 70-year lender floor and onerous ground-rent tests.
Overall rating
Long lease and non-onerous ground rent — low leasehold drag on saleability.
Headline
Lease at sale
85 yrs
Total carrying cost
£28,140
over 10 yr hold
Average annual cost
£2,814
Ground rent % of value
0.100%
>0.1% is onerous
Risk flags
Year-by-year carrying cost
| Year | Lease yrs left | Service charge | Ground rent | Reserve | Total | Cumulative |
|---|---|---|---|---|---|---|
| 1 | 95 | £1,800 | £250 | £300 | £2,350 | £2,350 |
| 2 | 94 | £1,890 | £250 | £300 | £2,440 | £4,790 |
| 3 | 93 | £1,985 | £250 | £300 | £2,535 | £7,325 |
| 4 | 92 | £2,084 | £250 | £300 | £2,634 | £9,958 |
| 5 | 91 | £2,188 | £250 | £300 | £2,738 | £12,696 |
| 6 | 90 | £2,297 | £250 | £300 | £2,847 | £15,543 |
| 7 | 89 | £2,412 | £250 | £300 | £2,962 | £18,506 |
| 8 | 88 | £2,533 | £250 | £300 | £3,083 | £21,588 |
| 9 | 87 | £2,659 | £250 | £300 | £3,209 | £24,798 |
| 10 | 86 | £2,792 | £250 | £300 | £3,342 | £28,140 |
Screening estimate, not a formal lease valuation — get a surveyor's RICS valuation before extending. For planning only, not advice.
Frequently asked questions
Answers to the questions UK property investors most often have about this tool and the underlying rules.
- Why does an 80-year lease matter so much?
- Below 80 years remaining, the cost of extending a lease includes "marriage value" — broadly half the uplift in the flat's value that the longer lease creates — payable to the freeholder on top of the rest of the premium. That makes extension noticeably more expensive, so a lease drifting under 80 (especially during your ownership) is a real value and saleability risk. The calculator flags when your lease starts under 80 or crosses the cliff before you sell.
- What counts as "onerous" ground rent?
- Lenders and conveyancers treat ground rent as onerous if it is disproportionate or escalates aggressively — common red lines include rent above roughly 0.1% of the property value, clauses that double more often than every 20 years, or rent over £250 (£1,000 in London) which can risk an assured shorthold tenancy trap. The Leasehold Reform (Ground Rent) Act 2022 cut ground rent to a peppercorn on most new long residential leases, but existing leases are unaffected.
- What lease length do mortgage lenders require?
- Most lenders want the unexpired term comfortably above 70 years — often expressed as the lease running at least 30–40 years beyond the end of the mortgage term. A lease that will fall under ~70 years while you own it shrinks your future buyer pool to cash buyers and specialist lenders, which is why the calculator projects the term to your sale date rather than only showing today's figure.
- Does this calculate the cost of extending the lease?
- No — a statutory lease extension premium depends on the flat's value, ground rent, term and capitalisation/deferment rates, and the rules are changing under the Leasehold and Freehold Reform Act 2024. This tool flags whether you are in marriage-value territory and how onerous the ground rent is, so you know when to get a formal valuation from a surveyor.