The notices of breach of contract were sent on September 30 to Beijing Innovative Linkage Technology (doing business as DNS.com.cn) in China and Joker.com in Germany.
The companies manage about 300,000 and 600,000 domain names respectively.
ICANN-accredited registrars are required to take reasonable steps to investigate Whois inaccuracy claims. But, in May 2008, following an audit, ICANN notified DNS.com.cn and Joker.com that it was concerned they were not making an adequate response to Whois complaints.
Despite assurances from both companies that they had suitable processes in place to investigate Whois data, ICANN disagreed and sent them notices of breach of contract.
The two registrars have 15 days to cure the alleged breaches, otherwise ICANN will take further action, including possibly terminating their contracts.
IP rights owners have long urged ICANN to get tough on registrars who do not provide adequate Whois information as it is essential in identifying the name and location of domain name pirates.