The government abolished stamp duty for all first-time buyer purchases up to £300,000 in November's Budget.
The relief is also available on the first £300,000 of the purchase price of properties up to £500,000, meaning an effective reduction of £5,000 for first-time buyers in high price areas such as London.
Chancellor Philip Hammond said the changes mean a stamp duty cut for 95% of all first-time buyers who pay stamp duty and "no stamp duty at all for 80% of first time buyers".
Speaking today, Theresa May said the changes have had an "immediate impact", adding: "I have made it my personal mission to build the homes this country needs so we can restore the dream of home ownership for people up and down the UK..
"We are building a Britain that is fit for the future and our message to the next generation is this - getting on - and climbing up - the housing ladder is not just a dream of your parents' past, but a reality for your future."
However Labour's shadow housing minister John Healey said that the stamp duty change would instead drive up house prices and warned that "the number of young home-owners is in free-fall".
Healey added: "Under the Tories the number of new low-cost homes for first-time buyers has halved and not a single one of the 200,000 'starter homes' promised has been built.
"After almost eight years of Conservative failure on housing, homelessness has doubled, home-ownership has fallen to a 30-year low and the number of new social rented homes is at the lowest level since records began. It's clear Theresa May has no plan to fix the country's housing crisis."