Workplace investigators are putting the squeeze on more than a dozen Top Juice outlets in four states after staff contacted them for help.
The Fair Work Ombudsman conducted "surprise audits" at 17 outlets in Victoria, NSW, Queensland and the ACT on Tuesday after receiving anonymous requests from Top Juice employees.
Allegations from staff include underpayments, failing to provide breaks, not providing proper pay slips or incorrect information on pay slips, and not paying termination entitlements.
"Our intelligence indicates that high numbers of migrant workers, international students and young people are employed at Top Juice outlets, who may be unaware of their workplace rights or unable to speak up due to concerns about their visa status," Fair Work Ombudsman Sandra Parker said in a statement.
"Our inspectors are on the ground to gather further information about Top Juice's operations and determine if there are any breaches of workplace laws."
Top Juice operates 75 stores across Australia, selling a variety of juices, smoothies and meals.