The TAB is being investigated by the Department of Internal Affairs following a text campaign that may have breached anti-spam law.
The two messages were sent before the All Blacks' two home Tri Nations test matches and said recipients could unsubscribe by replying STOP, with a "std msg fee" applying.
However New Zealand's anti-spam legislation requires no cost be associated with unsubscribing from commerical messages.
Hamish McConnochie, a Victoria University student, has filed two complaints, claiming the messages also breached the guidelines published on Internal Affairs anti-spam unit's website.
In June McConnochie attracted media attention after revealing Telecom had breached the law. Internal Affiars took no action because Telecom updated its terms and conditions.
"It's disappointing that we have these laws in place yet some of the largest companies and organisations in New Zealand seem unable to clearly comply," McConnochie said.
The TAB could face a fine of up to $500,000 but Internal Affairs generally issues a formal warning.