Manchester City sources insist the fee is fixed at £116 million with no add-ons, reports BBC Sport, though other reports suggest the total package could rise to as much as £130 million.
If that higher figure is confirmed it would surpass the £125 million Liverpool paid Newcastle United for Alexander Isak last summer and set a new British record.
Nottingham Forest held out through two rejected offers before City's third bid broke the impasse. Owner Evangelos Marinakis had been handling negotiations personally and was determined to secure a record fee. City's initial proposal of £85 million was turned down, as was a second bid comprising £106 million guaranteed plus £15 million in add-ons.
Anderson, 23, joined Forest from Newcastle United for £35 million in 2024 and made 88 appearances for the club, helping them reach the Europa League semi-finals last campaign. A medical has been arranged in the United States while Anderson remains on World Cup duty with England.
The midfielder said this week he has blocked out the transfer noise entirely. "It's pretty easy really — I'm just focusing on the present, I'm blocking it all out," he told BBC Sport.
"I've got a plan and it's to perform for England. I'm putting myself in the best position to cross the line and do that."
City sporting director Hugo Viana identified Anderson as the club's top midfield priority following the free transfer departure of Bernardo Silva. The signing sets a new Etihad record, surpassing the £100 million paid for Jack Grealish in 2021.
Forest have now turned their attention to signing two midfield replacements, with Tottenham Hotspur's Lucas Bergvall and Inter Milan's Davide Frattesi identified as targets.
Anderson is preparing for England's final Group L game against Panama on Saturday. His club future is settled — his international one is very much in progress.