Current law, 5% deferment rate, includes marriage value:

Lease Extension Calculator based upon the Leasehold and Freehold Reform Bill 2024

This calculator assumes that there is no marriage value to pay (decreasing the premium for some), however assumes a drop in the deferment rate to 3.5% - 4.5% (increasing the premium for some). The deferment rate is adjustable.

Leaseholders with leases ranging from 80 to 95 years will no doubt pay a higher premium under the new law if the deferment rate drops below 5%. This could be offset by the fact that freeholder's will likely have to meet their own costs (rather than the current position where leaseholders are obliged to pay), witht the exception of low value premiums. The government have not defined low value transactions at this stage.

See our article on Leasehold and Freehold Reform Act

Why could I pay more after the reform?

The deferment rate is currently fixed at 5%. A lower deferment rate increases the premium. The government's advisor and economist (Tim Leunig) has stated his opinion is that the rate should be 3.5%. This small drop in the deferment rate could mean some leaseholders, particular those with more than 75 years will pay a substantially higher premium.

Here's an extract from the government's minutes at a recent parliamentary debate:

See page 89 here Hansard - Government Dabate on Leasehold Reform.

and another...

Disclaimer: Users should not rely on our results to base a decision on extending their lease Results are provided for guidance only. LEaseholders should recognise that there is a large degree of uncertainty, even as of 25th May 2024 now that the Leasehold and Freehold Reform Bill has passed.