The "Dine and Discover" scheme gives adult residents four $25 vouchers to spend - two for local hospitality venues and two for cultural venues.

The scheme kicked off in late March and government data shows more than 4.2 million people in NSW have downloaded the vouchers to date.

However many have not used all four of their vouchers and Treasurer Dominic Perrottet said on Wednesday the scheme would be extended by a month.

The vouchers - through the Service NSW app - will now expire on July 31.

"People of all ages and walks of life are giving them a go and we don't want anyone to miss out," Mr Perrottet said in a statement.

"This extension will ensure everyone has a chance to use all four of their vouchers, which I'm sure will be particularly handy in the school holidays."

Patrons using their hospitality vouchers spend an average of $16 on top of their $25 voucher when dining out, government data shows.

More than five million vouchers have been used to date in hospitality venues, while 1.2 million have been used in movie theatres and almost 370,000 vouchers have been cashed in at museums and art galleries.

The $500 million voucher scheme was the centrepiece of the government's November budget, aiming to get more people spending amid COVID-19.

Australian Associated Press