Championship clubs are allowed to register 25 players aged 21 and above.
Loan players, irrespective of age, also have to fit into that squad size.
The arrivals of Ali McCann and Josh Murphy late on deadline day took the number of senior players to 29.
Clubs have until tomorrow to register their squads with the EFL.
Until the January transfer window, they can only make a change to the squad in the event of a serious injury, that being in agreement with league officials.
North End’s 29 senior pool includes Izzy Brown who is out until later in the season with a ruptured Achilles tendon.
He won’t be registered for the first-half of the season, so three more won’t be playing Championship football.
PNE are carrying four senior keepers, which points to Connor Ripley being left out of the 25.
So there will be two outfield players left out and there could be a third if North End want to leave room for the potential signing of Connor Wickham.
The striker is training with Frankie McAvoy’s squad in a bid to earn a contract.
As a free agent having been released by Crystal Palace in the summer, Wickham can sign for a club outside of the confines of the window.
North End left it late on Tuesday night to bring in McCann and Murphy.
McCann joined from St Johnstone in a £1.2m move, with Murphy arriving on a season’s loan from Cardiff.
Murphy has met his new team-mates but McCann will have to wait until later next week for his introductions.
The 21-year-old midfielder is on international duty with Northern Ireland and has three World Cup qualifiers coming up – tonight, on Sunday and next Wednesday.
A number of clubs were chasing McCann, with Rangers and Celtic linked earlier in the summer.
North End got their man just before the deadline, the Edinburgh-born player set to intensify the competition in PNE’s midfield.
Importantly, he can play the shielding defensive role which Ben Pearson used to provide.
St Johnstone say that potentially, McCann can be their record sale.
The deal with North End includes various add-ons.
Saints chairman Steve Brown said: “We tried very hard to resist all of the bids for Ali.
“But Preston’s offer is a huge sum and one we couldn’t turn down. In time, it is likely to become the club’s record transfer fee received.”
Support us and become a subscriber today. Enjoy unlimited access to local news, the latest football stories and new puzzles every day. With a digital subscription, you can see fewer ads, enjoy faster load times, and get access to exclusive newsletters and content. Click here to subscribe.