Farmers have until 18 January to accept or decline the Rural Payment Agency's funding offer as part of the Countryside Productivity Small Grant scheme.
More than 3,800 farmers are set to benefit from £21m in new equipment as part of the third and final round of the CPSG scheme.
Grants of between £3,000 and £12,000 are issued to farmers so they can invest in new and innovative equipment.
These can range from livestock monitoring cameras to precision farming technology - items that aim to help farming businesses save money and boost productivity.
But time is running out for successful applicants to let the agency know that they want to proceed to the next phase of the scheme.
The NFU has told farmers that if the RPA does not receive acceptance by this date, they will withdraw the Grant Funding Agreement offer.
After applicants have accepted the offer, they have until midnight on 31 May to buy the equipment and have it installed, and then submit their claim for payment.
This claim deadline was extended by two months - from 31 March 2021 - to allow for potential delays caused by the impacts of the coronavirus pandemic.
The NFU explains that farmers cannot complete this second phase without first accepting the Grant Funding Agreement offer via the online portal by 18 January.
"Once farmers have accepted or withdrawn the Grant Funding Agreement, they will receive an email confirming this from the RPA," the union says.
"If you want to withdraw after the deadline, you can email the RPA giving your reference number the RPA has previously given you."