Barry McGuigan tore up a cheque for boxer Carl Frampton, Belfast High Court has heard.
Mr McGuigan is accused of trying to conceal and control payments to the fighter.
Mr Frampton, 33, is suing his ex-manager and Cyclone Promotions for alleged withheld earnings.
Mr McGuigan is claiming against the Belfast-born boxer for breach of contract after their partnership ended in 2017.
Both men deny the respective allegations against them.
Fees and purse arrangements came under scrutiny on day 13 of their multi-million pound legal battle.
Mr McGuigan was pressed on disputed payments for the first fight against Leo Santa Cruz in July 2016.
Mr Frampton won the contest in New York to become world featherweight champion.
Although Mr Frampton's fee was listed as $500,000 (£384,000), the court heard his actual purse was to be $1.5m.
A cheque for $500,000 was said to have been given to the boxer near the dressing room after the contest.
Mr Frampton's barrister, Gavin Millar QC, told the court: "You told the US promoter who had given him that cheque that all monies had to come through you, and you ripped the cheque up."
But Mr McGuigan insisted: "That's complete cobblers, that's rubbish.
"I handed the cheque back to him and I didn't mention anything about money going to me."
Asked why he returned it, he said: "Because that wasn't the true figure, he knew that, and he was going to wire the money on obviously.
"The purse wasn't $500,000, that was just what we declared."
Mr Millar continued: "On our case, which is that you tore the cheque up, the reason that you did that was that you wanted to receive the money as Cyclone so that you could control the money."
The boxing manager responded: "That's just not true. We always received the money and then we paid Carl."
He also rejected allegations Mr Frampton was kept in the dark about the total purse, saying he knew it was a $1.6m pot, out of which he would get $1.5m.
Attention then turned to the rematch with Santa Cruz in January 2017, when the Mexican defeated Mr Frampton to reclaim the title.
A sparring partner had to vacate his bedroom at their rented house in Las Vegas for members of the McGuigan family, the court heard.
Counsel then put it to him: "One of the things you bought and are claiming as an expense for this fight is an inflatable mattress."
Mr McGuigan said he did not remember but accepted the assertion.
Challenged on its legitimacy as a fight expense, he added: "The guy had to sleep somewhere."
Earlier, the court heard total travel and subsistence expenses of £75,000 were listed for Mr Frampton's world title fight against Scott Quigg in Manchester in February 2016.
The figures included a bill for just over £20,000 from the Midlands Hotel in the city.
Asked who was staying in the 41 rooms allegedly booked, Mr McGuigan said: "Members of the Cyclone team, members of Carl's family, members of my family, so quite a few people here."
A total invoice for up to £15,000 from a Manchester cocktail bar was also scrutinised.
When it was suggested the bills went to the issue of the fight's profitability, Mr McGuigan said: "I understand these expenses were all totted up, and then Carl had to pay a part of that expense, but he didn't pay quite a considerable amount."
The case continues.