Cartman, who has found the back of the net at regular intervals throughout his career, joins skipper Michael Coulson, midfielder Ryan Watson and player/assistant manager Michael Ingham in new boss Jono Greening's squad.
Greening said: "I spoke to Nathan last weekend, he is passionate about staying and banging goals in. I love his attitude.
"He wants to train and play and hopefully he'll get us a lot of goals this season.
"I'm looking forward to working with him in pre-season, I want him to start the season with a bang and hopefully Carts will fire us to promotion.
"Things are shaping up nicely, but there is still a bit to go.
"We start pre-season training next week, so I'll be able to have a good look at a few players and maybe sign a few up."
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