Chief executive Bradley Gerdis said it was speaking out about the issue because of concerns that it would impact ordinary Kiwis as well as retailers.
"We feel it is important that we step up and make a concerted effort to inform all retailers - not just our customers of the changes because this will impact all New Zealanders."
He said Smartpay was working with payment network operator Paymark to establish which of their customers have terminals that need upgrading and will automatically upgrade all its retail customers.
But Retail New Zealand says the concerns are overblown and there is still plenty of time for retailers to switch over.
Retail New Zealand spokesman Greg Harford said he believed most retailers were aware the change was coming and there was still another six weeks before it kicked in.
"There's no need to panic."
He said most retailers leased their equipment and suppliers were responsible for ensuring new equipment was brought in.
Harford said he had not heard any widespread concerns about retailers not being ready for the April 30 change.
"It has been pretty well signalled."
He expected suppliers to be well geared up for the change.