The Department of Internal Affairs claims Sky City has not complied with its anti-money laundering programme.
The alleged failures span from February 2018 to March last year, and include not properly monitoring its accounts and transactions.
Internal Affairs says it's not suggesting Sky City was directly involved in money-laundering, but casinos can be an attractive way for criminals to launder the proceeds of crime.
It says casinos must have robust processes in place to protect them from misuse.