Newcastle's resolve has finally been broken by a £125 million Liverpool bid.
The Magpies are expected to report Isak's sale as a £130m capture by the Reds due to a bonus cost-saving, according to reports.
Newcastle have replaced Isak with VfB Stuttgart forward Nick Woltemade and, pending a medical, will announce Yoane Wissa's arrival before the transfer deadline at 7pm.
Newcastle make £5m cost-saving on Alexander Isak to Liverpool deal
Eddie Howe's side have started Anthony Gordon and Will Osula in recent fixtures due to Isak's self-imposed absence.
The player has had his heart set on a move to Anfield, although Newcastle had previously taken a hard line with the attacker, rejecting a £110m proposal from Liverpool.
Arne Slot's Reds may yet add another signing this transfer deadline day with the addition of Marc Guehi from Crystal Palace.
Should they complete business for Isak, it will take the Reds' summer transfer spending above the £500m mark, following the arrivals of Florian Wirtz, Hugo Ekitike, Jeremie Frimpong, Milos Kerkez and Giorgi Mamardashvili.
Newcastle's Isak sale will become the British transfer record, consequently smashing the club's individual transfer record for funds earned from a player's departure.
The north-east club are not understood to be paying Isak a loyalty bonus, which is customary in transfers, as a result of this summer's ongoing saga and the player's decision not to go on pre-season tour.
This is reportedly set to save Newcastle £5m, hence the discrepancy in the reporting of fees.
Newcastle have added Malick Thiaw, Jacob Ramsey, Aaron Ramsdale and Anthony Elanga in addition to Woltemade's arrival this summer.
