Demonstrators banging pots and pans and wielding megaphones marched on the restaurant calling for fair pay for staff, alleging a former chef was owed thousands in backpay by the owners.

United Voice, the union behind the rally, lodged a claim for $21,000 with the Federal Circuit Court on Thursday claiming former kitchen staffer Rainier Storm was denied proper rates of pay, holiday and weekend loadings and was not given adequate breaks during long shifts.

According to the court documents, Mr Storm was paid around $2 an hour less than the award base rate of pay from 2013-2014, regularly worked weekends but was not always paid shift penalties and was not paid extra for working more than 11.5 hours a day or 38 hours in a week.

Mr Storm said the restaurant had developed a culture that discouraged kitchen staff from taking the breaks they were entitled to. "I guess you'd call it the dark side of hospitality," Mr Rainier said.

United Voice ACT branch secretary Lyndal Ryan said underpayment and failing to give workers their legally entitled breaks was not uncommon in Canberra's restaurants.

"Every time the Fair Work Ombudsman does an audit they identify problems, and we actually have a lot of parents contact us complaining that their children are not being paid properly, but they're obviously too scared to complain," Ms Ryan said.

"Rather than encouraging pay cuts for workers who give up weekend time with family and friends to work for them, Restaurant and Catering Australia should be encouraging their members to do the right thing by their staff," Ms Ryan said.

Restaurant and Catering Industry Association chief executive John Hart said his organisation spent the bulk of its time educating members and helping them to comply with the complexities of the awards system.

"I would estimate that the rate of non-compliance is quite high, especially when you're talking about things like travel and tool allowances buried deep within the awards. It's an incredibly complicated system with laters of overlapping legislation, so it's no wonder small business owners are not getting it right all the time," Mr Hart said.

Mr Hart said most non-compliance was unlikely to be willful, and the best way to address it was to simplify the systems to make them easier to understand.

A Penny University manager was contacted but declined to comment.