The property purchase tax has been suspended on the first £500,000 of all sales in England and Northern Ireland since July.The tax break for will now continue until the end of June.
After that the nil rate band will be set at £250,000 - double its standard level - until the end of September.
Rishi Sunak told MPs the extra move was "to smooth the transition back to normal - and we will only return to the usual level of £125,000 from October 1".
The stamp duty holiday was introduced to help buyers who might have taken a financial hit because of Covid. It was also intended to boost a property market hit by lockdown.