Midfielder Carter and defender Tozer will be joined in leaving Sixfields by Matt Duke, Lee Collins, Lewis Hornby, Ross Perry, Ian Morris.
Ex-West Brom midfielder Carter made 27 appearances for Northampton this season while Tozer will leave as the club cannot afford to carry his wages.
John-Joe O’Toole and Chris Hackett have also been transfer-listed by the League Two side.
“It’s a tough part of the job for any manager but we have to make professional decisions to take the club forward,” boss Chris Wilder told the club’s official site.
“You have to make decisions as a manager and we thank all the players for their efforts.
“They’ve been good for me and I think we as a club have been good to them.
“Darren Carter hasn’t really played any football all season and he wants to play.
“Ben Tozer is on an excellent contract and he deserved that under the previous manager.
“He hasn’t been able to get into the team because of the form of Brendon (Moloney) and I can’t afford to carry two right-backs on the wages that they are on.”
No decision has been made on goalkeeper Shwan Jalal who arrived on a short-term deal in February while Billy Bodin and Tom Newey will hold talks with the club subject to their fitness.
And Wilder is eager to shape his squad but bringing in new players early.
“We are already in discussions with our targets and we want to get our business done early,” he said.
“We will look at the loan market but I’m not a big lover of short-term loans and if we do bring players in on loan it will be for the season or from window to window.”