The floods may have impacted some numbers but there are still reports across the state where mice have persisted.

That's why the NSW government will today announce that the mouse rebates for farmers, small businesses and households have been extended into 2022.

Primary producers will now be able to make multiple claims for zinc phosphide purchases, up to the $10,000 cap.

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Already more than 52,500 households and 6500 small businesses have taken advantage of this rebate worth more than $31 million.

Deputy Premier Paul Toole said the changes ensured the mouse bait rebates would benefit those in the bush who need it most ahead of a potential post-harvest surge.

"The reports we are getting indicate mice numbers are down, but we can't be complacent, which is why we've extended the deadline," Mr Toole said.

Toby O'Brien, who is the team leader of invasive species and plant health for Riverina Local Land Services, said there were still reports of mice in his region and landholders needed to be vigilant.

"With floods delaying harvest there is residual grain and grain left in the paddocks, which has the potential for mice numbers to breed up," Mr O'Brien said.

He urged landholders to use the mouse chew cards to report results online to help make management decision. Mouse chew cards are soaked in canola or linseed oil and are set in paddocks to see what proportion of the card has been chewed by mice.

"The situation on the ground is that farmers are our eyes and our ears and need to report activity. By detecting mice early it is critical to impacting numbers and is essential before mouse control can be rolled out," he said.

Under the changes, households and small businesses will have until January 31 to claim up to $500 or $1,000 respectively to help meet the cost of mice baits, traps and cleaning materials bought after February 1, 2021. Primary producers will have the same time to claim.

NSW Agriculture Minister Adam Marshall said the government would work closely with bait manufacturers to ensure there was enough zinc phosphide concentrate available to produce the bait farmers need to protect harvest.

"Now is not the time for farmers to be doing paperwork, they should instead be focused on managing their properties through harvest and rain events," Mr Marshall said.

"Although the number of mice has reduced, it is critical to make this harvest as clean as possible to reduce available food and shelter - which is why we've extended the deadline for applications."