The 24-year-old moves to the National League South club as they chase promotion.
He was loaned to Woking in early October by the Stones and and his goals helped keep them in title contention.
Now he will hope to get Billericay back moving in the championship race.
Blues manager Dean Brennan says he is "thrilled" with the signing.
Maidstone's chief executive Bill Williams said: “We’re sorry to see Jamar go but football never ever stands still.
"This move is something that Jamar wanted to happen and the club wishes him well in the future.”