Swindon have failed to sign Paul Benson from Charlton after their paperwork reached the Football League after the deadline.
The Robins had agreed a deal to bring the 32-year-old to the County Ground, only for the relevant paperwork to fail to reach the Football League ahead of the 5pm deadline last Thursday.
The club had hoped the move would still go through after talks with the League, but they will now have to wait until the January transfer window to get their man.
Chairman Jeremy Wray told the club's official website: "It was always going to be a scramble to get all of the paperwork assembled and submitted within the very tight time-frames we had to work with.
"We held lengthy discussions with the Football League trying to persuade them to afford us a limited degree of leeway, but rules are rules and, in the final analysis, we sadly fell outside of them and, therefore, have to adhere to the Football League ruling.
"(It is) very disappointed for all concerned but hopefully we can revisit the Paul Benson registration in January 2012."