Louis Wells is heading back to Dartford after Margate accepted an approach for the goalkeeper.
Wells joins promotion-chasing Darts ahead of Thursday's transfer deadline and Gate have already moved to sign a replacement.
They've brought in Kleton Perntreou from Worthing, the new man having also played for Chatham in the Southern Counties East League this season.
Bailey Vose has been Dartford's first-choice goalkeeper since long-serving Deren Ibrahim left the club earlier this season to take up a coaching role at Charlton Athletic.
Vose, on loan from Colchester United, has made 23 appearances for the Darts in National League South but the League 2 club have a 24-hour call-back option on the 20-year-old.
Dartford joint-boss Jamie Coyle said: "We had a bit of a scare last week when Colchester's goalkeeper got injured and he was potentially going to get called back.
"We were planning on getting a goalkeeper dual-registered just in case there were injuries after the deadline but we've done it a bit sooner than we'd planned because of the scare last week.
"It's good healthy competition and a lot of the teams in play-off positions are now running with a goalkeeper on the bench.
"Between now and the end of the season, each game is so vital so it's really important we've got two goalies available for every game.
"The agreement we've got with Colchester, they can call him back in 24 hours so it doesn't give you any time to get a replacement.
"With the deadline coming up tomorrow, we'd be stuffed and throwing in Ben Greenhalgh - which we don't want to do!
"The good thing about Louis is he's very experienced and he's someone both of us have played with before.
"He was with Flans last year at Concord and he'll be good to have around the changing-room.
"He's been there and done it, in the play-off environment and promotions as well. He's an old head we're excited to bring into the squad.
"We've got one or two other players we're looking to dual-reg before the deadline just to cover for the play-offs in case we get injuries."
Vose remains the No.1 at Dartford with six games of the regular season remaining.
Coyle said: "Bailey's been outstanding. I went through nine goalkeepers last season (at Welling) and had the worst time ever.
"But he did extremely well for me last season and for a 20-year-old kid to come in and do what he's done this year, it's testament to him.
"I'm pleased for him because he's made some really important saves and contributed to a lot of points that we've won over the season."