The scheme is available until 2021, and you'll need a five per cent deposit. Buyers who save for a deposit through a ‘Help to Buy ISA' account can also benefit from a 25 per cent bonus of up to £3,000 to supplement £12,000 of savings. This bonus is credited over time: for each £200 saved, buyers will receive £50, but you have to save up at least £1,600 before claiming the extra payment.