Jean-Claude Perrottet - the younger brother of former NSW Liberal premier Dominic Perrottet - said he did not know why he was paid the money on several occasions throughout 2021, but agreed it was a sizeable amount.
The NSW Independent Commission Against Corruption is investigating alleged illicit political donations and branch-stacking spearheaded by the Reformers, a conservative Christian faction among state Liberals.
Hotelier Michael O'Hara earlier told the commission he agreed to support the Reformers via monthly $5000 donations paid to a consultancy firm called Beckington, owned by the group's co-founder Christian Ellis.
Mr O'Hara was legally prohibited from giving political donations due to associations with the liquor and gaming industries.
Mr Ellis would issue Mr O'Hara with false invoices for consultancy services, the inquiry heard.
Throughout 2021, as Mr O'Hara paid monthly instalments to Beckington, the younger Perrottet received payments for the exact same amount into his account.
Following an initial payment of $1000 in January 2020, Jean-Claude Perrottet received $5500 in April 2021, followed by $5000 payments in May, June and July of that year, the commission heard.
Counsel assisting Juliet Curtin suggested there was an arrangement that involved Mr Perrottet being paid a portion of the money Beckington received from Mr O'Hara.
"I don't recall whether there was an arrangement," Mr Perrottet said.
Ms Curtin said it was "strange you don't recall" receiving those payments.
"I don't know how many different ways I can tell you I don't recall," he replied.
Mr Perrottet agreed the amounts were sizeable, adding he had potentially done some work for Beckington or Mr Ellis might have owed him money.
The now 29-year-old Jean-Claude Perrottet was approached by Mr Ellis and the other founder of the Reformers, Robert Assaf, in 2018 and asked if he wanted to join them, the commission heard.
The group organised events around social issues intended to attract like-minded people to the Liberal Party, with topics including abortion, euthanasia, religious freedom and government-mandated vaccinations.
Part of the Reformers' strategy was to sign new members to branches they wanted to control.
Mr Perrottet said he was not sure whether he had any awareness of political donation laws at the time, describing going to branch meetings as "like having a cup of tea with some people from the bowling club".
"You were crunching numbers for various different branches, not just having cups of tea," Ms Curtin said.
Mr Perrottet also faced questions over funds paid by Catholic Schools NSW to Beckington, which Ms Curtin suggested was to support the work of the Reformers.
He said his understanding was Mr Ellis was providing services for clients through Beckington and then supporting the Reformers himself through the company.
"I want to suggest to you, Mr Perrottet, you're not being entirely truthful with that answer," Ms Curtin said.
Ms Curtin suggested Mr Perrottet was aware the former head of Catholic Schools NSW, Dallas McInerney, was paying funds from the organisation to Beckington to support the work of the Reformers.
"I'm not aware of me being aware of that," he replied.