The royal commission into trade unions has turned its attention to so-called fighting funds comprised of payments from Transport Workers Unions (TWU) staff.
The inquiry is sitting in Sydney to examine union-linked funds used to support candidates in union elections.
Counsel assisting the commission Jeremy Stoljar SC said one, known as the Team Fund, contained about $260,000 contributed by officials and employees of the Victorian and Tasmanian branch of the TWU.
Mr Stoljar said it was a "matter of some dispute" whether contributors volunteered to make payments or were required to.
He said the hearings would also explore whether the money was used "for the personal benefit of the signatories".
Former branch organiser Arthur Wood told the hearing he contributed to the fund for 12 years.
He said he believed the money would be used in contested elections, but he began to question that over time.
"It was after we'd had a bit of a run with no [contested] elections, we were sort of wondering how much money do we have and why are we still contributing when there must be a hell of a lot of money in that account," he said.
After he stopped work in 2010, some of his money was returned when he asked for his payments to be refunded.
Mr Wood said the deductions were not itemised on his payslips.Fund 'helped TWU secretary fight ALP campaign'
The commission is also looking at the TWU-linked Transport, Logistics, Advocacy and Training Association.
Mr Stoljar said its bank accounts held about $142,000 as of May this year, most of which had been raised through functions.
He said $5,000 from the account was used to support TWU national secretary Tony Sheldon's campaign for the position of federal president of the Australian Labor Party.
Mr Sheldon has been listed as a witness to appear sometime in the next three weeks.
The three-week Sydney hearing is investigating funds associated with the TWU and the Shop, Distributive and Allied Employees Association (SDA).
The Fair Work Commission's Regulatory Compliance Branch Director, Chris Enright, said in a statement to the commission that "while not all unions have 'fighting funds', many office holders and employees of unions operate them, in some form or another, at various times during election cycles".
"Fighting funds are said to be analogous to Christmas Club or social club funds which are created from the voluntary contributions of members of organisations with shared goals."