Opposition Leader Bill Shorten has denied he was waiting to see whether a $40,000 donation to his 2007 election campaign would emerge in the trade union royal commission before deciding to declare it this week.

Counsel assisting Jeremy Stoljar tabled a letter on Wednesday showing a campaign donation, dating back to the 2007 federal election, was only fully declared to the Australian Labor Party (ALP) and Australia's electoral watchdog on Monday.

The letter, from Mr Shorten to ALP official Kosmos Samaras, details more than $40,000 received by Mr Shorten to pay for the services of a campaign manager.

The former Victorian and national head of the Australian Workers Union, who appeared before the commission for the first time on Wednesday, faced questions over several cases raised so far at the hearings, including claims about deals that were allegedly detrimental to workers but helped business.

Key points: Counsel assisting Jeremy Stoljar produced a letter showing Bill Shorten waited until this week to fully declare more than $40,000 in campaign funding from the time of the 2007 election, which saw him transition from AWU boss to federal MP

Counsel assisting Jeremy Stoljar produced a letter showing Bill Shorten waited until this week to fully declare more than $40,000 in campaign funding from the time of the 2007 election, which saw him transition from AWU boss to federal MP Mr Shorten denied he was waiting to see if the issue would come up in the royal commission before filing the return, saying he only found out about the oversight "a few weeks ago"

Mr Shorten denied he was waiting to see if the issue would come up in the royal commission before filing the return, saying he only found out about the oversight "a few weeks ago" The money relates to the services of Lance Wilson, a campaign manager on Mr Shorten's team whose wages were paid by labour hire company Unibuilt

Mr Stoljar began proceedings by asking Mr Shorten about documents relating to his 2007 campaign director Lance Wilson.

The commission heard Mr Wilson worked as Mr Shorten's campaign director between February and November 2007, when Mr Shorten was elected.

Mr Shorten was asked whether Mr Wilson was a research officer at a labour hire firm called Unibuilt, as documents seemed to suggest, or actually working on his campaign.

"I cannot explain why that particular title was used — he was a campaign resource and campaign director for me," Mr Shorten said.

Mr Shorten confirmed the arrangement was that Unibuilt would pay Mr Wilson's wage but that he would work on Mr Shorten's campaign.

Sorry, this video has expired Shorten rejects allegation of personal advantage in AWU deal

"It was the donation by Unibuilt of a person to work on my campaign, that's correct," he said.

Mr Stoljar said documents showed Unibuilt paid a total of about $40,000 of the $52,000 paid to Mr Wilson for his work on Mr Shorten's campaign.

Another $12,000 was invoiced to Unibuilt by the union but never paid by the company.

Mr Stoljar also alleged Mr Shorten failed to disclose the donation of Mr Wilson's campaign work to the Australian Electoral Commission (AEC).

Mr Shorten said Australian Labor Party (ALP) advice was to detail donations via a return to the ALP, though he admitted there was an "incomplete" form sent to the party's headquarters at the time, an oversight he said was rectified "within the last 144 hours".

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 5 minutes 26 seconds 5 m Bill Shorten makes his appearance at the trade union royal commission. Download 10 MB

"I have discovered in very recent times that there was an incomplete form sent to the ALP head office and that is — I take ultimate responsibility for that," Mr Shorten told the commission.

"This is done by my campaign director each year and we have now updated it."

Mr Shorten said the incomplete disclosure was discovered when he was "going back and checking matters" in preparation for his royal commission appearance.

Sorry, this video has expired Bill Shorten answers questions on 2007 campaign donations

Those discoveries were made "weeks, maybe months" before the declaration was amended last week, he said, adding that he wanted to make sure the disclosure was done right the second time around.

"Were you waiting to see whether this would emerge at the royal commission," Mr Stoljar asked.

"Not at all," Mr Shorten replied.

Asked if he obtained the authority of AWU members for the Unibuilt campaign donation arrangement, Mr Shorten replied: "The secretary of the union has the authority to commit resources to political campaigning."

Shorten denies seeking personal advantage in AWU deal

Mr Shorten said Unibuilt would not have expected anything in return for supplying Mr Wilson's services to the campaign.

He hit back at an accusation from Mr Stoljar that he used his position as AWU national secretary to his advantage — that is, to obtain the donation of a campaign worker.

"Absolutely not," Mr Shorten said. "I completely disagree with what you said just then.

"You have made a pretty significant statement and I wouldn't mind having the courtesy to finish that because I completely disagree with what you just said then.

"To me, what that does is that assumes that whenever there is a donation in our electoral system, by anyone, that all other relationships and transactions must immediately be cast into doubt.

"That is not right and that is not how I operated at the union."

Mr Stoljar asked Mr Shorten about invoices the AWU sent to Unibuilt in 2007 for Mr Wilson's work that, counsel assisting said, "didn't truly and accurately reflect" his job.

"How the union conducted its relationship, in terms of invoicing, with the company is just not a matter which I was directly involved in," Mr Shorten replied.

Mr Shorten said he was not involved in negotiating an enterprise bargaining agreement (EBA), also in 2007, between the union and the company as he was no longer Victorian state secretary at the time.

Mr Stoljar said: "It would profoundly weaken the bargaining position of the AWU if, in negotiating with a company about an EBA, that company is at the same time making a donation to the national secretary's political campaign. Do you agree with that?"

Mr Shorten replied: "No, I don't."

I can't recall beer at firm's Melbourne Cup marquee: Shorten

The trade union royal commission has been looking at whether the AWU artificially inflated member numbers by charging cleaning company Cleanevent $25,000 a year for workers' member fees.

Sorry, this video has expired I'm not sure if I 'dropped in for a beer' at firm's Melbourne Cup event, Shorten says

Among allegations raised was that AWU struck a deal with Cleanevent that saw cleaners paid below award wages for working at prestigious events.

On Wednesday, Mr Shorten confirmed he negotiated with the firm in his role as an organiser with the AWU.

The Opposition Leader said he could not confirm if he "dropped in to have a beer" at a Cleanevent marquee at the 2006 Melbourne Cup.

"I can't even remember who won," he said of the race.

Mr Shorten, while acknowledging that EBA negotiations were ongoing with the company at the time, became visibly frustrated at the line of questioning.

Shorten: I don't know if I dropped in there to have a beer. I wouldn't put it beyond myself to drop in to have a beer, but also I have to say I like going to the races — I think the Spring Carnival is an excellent time of year. Stoljar: Who gave you the passes? Shorten: That's my personal business. It's my wife. My then-wife gave it to me. Stoljar: Did you discuss the EBA negotiations when you dropped in on [Cleanevent boss] Craig Lovett? Shorten: In terms of my negotiations ... I'm most professional. The sheer idea that two people in a negotiation may see each other periodically, socially, is not an indicator [of any wrongdoing] ... I don't know if lawyers on different sides of arguments might play golf together.

Mr Shorten denied knowledge of a "side deal" with Cleanevent to have the firm pay $25,000 worth of union fees, saying he only became aware of the deal "in very recent times".

He said he could not say whether Cleanevent employees needed to tick an "opt-out" box on job applications to avoid being signed up to AWU.

"What I can promise you, Mr Stoljar, is I wasn't forcing people to be in the union," he said.

Outside the royal commission, former Labor minister Greg Combet said Mr Shorten sufficiently answered every question that was put to him.

"I've got to say it's the first time that I've seen a union official grilled for not being sufficiently militant at a royal commission," he said.

"Usually these royal commissions are getting stuck into union officials for going too hard, and I think that sort of hypocrisy just underlines the political nature of this royal commission."

Mr Shorten, ahead of his appearance on Wednesday, hit back at Government criticism of his time at the AWU, saying he would "put my record against Tony Abbott's anytime".