Amorim is yet to speak publicly about his time at United and sources close to the 41-year-old have said there is no immediate likelihood of that changing.
The payment completes an expensive managerial experiment that ultimately ended badly.
United confirmed in a similar filing on 27 November 2024 they were paying Sporting £11m to hire Amorim to replace Erik ten Hag, whose exit was costing £10.4m.
It means the combined changes around Amorim could cost £37.3m.
His 14-month stint in charge was the shortest reign of a permanent manager at Old Trafford since David Moyes was sacked just eight months into his tenure in 2014.
Amorim won 25 of his 63 games in charge, finishing 15th in the Premier League, United’s worst performance since they were relegated in 1973-74.
They also lost the Europa League final, meaning they have no European football this season for only the second time since 1990.
This term, Amorim’s team were embarrassed by League Two Grimsby, who beat them on penalties in the Carabao Cup second round.
United were sixth in the Premier League when he was dismissed, having had a major fallout with director of football Jason Wilcox days before the Leeds game.
Although under-18s coach and former United midfielder Darren Fletcher was named as interim boss for two games, Michael Carrick has been given the job until the end of the season and won his fifth game out of six when his team beat Everton on Monday.
They are now fourth, and well placed to qualify for the Champions League.
Meanwhile, United have also confirmed they have increased the available credit from their drawdown facility by £50m to £400m, while also paying off £75m, meaning they currently owe £215m on it.
In addition, the filing also stated £600,000-worth of “sponsorship services” had been provided to Ineos Automotive Ltd, an offshoot of the Ineos group owned by United’s minority shareholder Sir Jim Ratcliffe.