Customers are able to login to the Mt. Gox site and check their balances. A notice on the site says:
This balance confirmation service is provided on this site only for the convenience of all users. Please be aware that confirming the balance on this site does not constitute a filing of rehabilitation claims under the civil rehabilitation procedure and note that the balance amounts shown on this site should also not be considered an acknowledgment by MtGox Co., Ltd. of the amount of any rehabilitation claims of users.