[3] He began his career at his father's plant hire firm,[4][5] and later at 21 secured a bookmakers licence and took a pitch at Limerick Greyhound track.

[10] McManus is also the primary director of Liberties Strategic Services, a family private office based in Geneva and Hamilton, Bermuda.

In 2024 McManus won the Grand National for a third time with his horse I Am Maximus, ridden by Paul Townend and trained by Willie Mullins.

[31] McManus, alongside fellow racing owner and businessman John Magnier, first invested in Manchester United in July 2000 buying 9.8 million shares for around £20million via a British Virgin Islands holding company Cubic Expressions.

In 2001, the pair further increased their investment in Manchester United to a total shareholding of 9 percent, taking them to the second largest owners behind BSkyB.

[34] However, outside of their controlling shareholding, McManus and Magnier were involved in a row with manager Sir Alex Ferguson relating to the ownership of a successful racehorse Rock of Gibraltar.

The first event took place at Limerick Golf Club, attracing professionals including Philip Walton, Des Smyth and Brian Barnes raising €1.5m for charity.

This led to major golfers including Jim Colbert, Bob Murphy and Tom Wargo from the PGA Senior Tour taking part.

The final event at Limerick Golf Club took place in 2000, where 15,000 fans watched as professionals such as Tiger Woods and Padraig Harrington played alongside celebrities including Sir Alex Ferguson and Formula One team boss Eddie Jordan.

Professional golfers including Tiger Woods, Ernie Els and Davis Love III played alongside stars such as Michael Owen and actor Peter Gallagher.

In July 2019, the aircraft was involved in an emergency landing at Shannon Airport following engine failure on a routine flight to the UK.

[59] He also owns an Agusta Westland AW139 helicopter registered EI-LIM and finished with green and yellow to match his racing silks.

A keen golfer, McManus has twice won the teams challenge at the Alfred Dunhill Links Championship in Scotland alongside professional Padraig Harrington.

It was also noted that a necessary change in charity status of the International Rugby Experience, if handed over to the council, could incur a VAT liability of €12 million.

[75] Following donations in 2018 and 2023 to the GAA, McManus faced criticism from journalist Mick Clifford who compared him, unfavourably, to an absentee landlord.

[76] The 2023 donation was also criticised by former Gaelic football player and commentator, Joe Brolly, who characterised it as an "act of self defense" to deflect from criticism of McManus' tax exile status.

[78][79] After McManus won the rights to host the 2027 Ryder Cup at Adare Manor, he wrote to Limerick City and County Council objecting to proposals to impose property tax on a plot with residential zoning in the estate arguing that the land in question is earmarked for a Ryder Cup bus terminal and should therefore not be taxed.

[82] According to the Glackin Report,[83] Hoddle Investments (the vehicle through which the deal was handled) executed two contracts with Telecom Éireann for the sale of the Johnston Mooney & O'Brien site for an aggregate price of £9.4 million, on 7 May 1990.

[84] The report concluded that McManus was a beneficiary of the sale of the site to Telecom Éireann, and received £500,000 in cash from the transaction, which Dermot Desmond had stored in a tennis holdall in his safe.