Treasury will issue a Customer Service Number (CSN) to active SBT taxpayers that have filed form C-8000, C-8030 (for registered taxpayers) or C-8044 in the last two years in time to file their SBT return(s). The CSN is not used when e-filing Michigan Business Tax (MBT) returns. The CSN is:

• Eight digits comprised of one alpha character and seven numbers.
• Case sensitive and the letters "I" and "O" are not used, and
• Used in conjunction with shared secrets to sign your e-filed SBT return when using the SBT Direct e-file Program.

Treasury no longer mails CSN letters to eligible SBT filers. Therefore, if the taxpayer is filing a second return with Treasury within the last two years, the taxpayer's CSN will need to be obtained from Treasury's Web self service at www.michigan.gov/bustax. If you are having difficulty obtaining your CSN, please use the "Ask A Question About My SBT Account" option.

Please keep your CSN on file, as you will use the same number for future filings of your e-filed SBT returns.

If you lost or misplaced your CSN use the "Check My Business Tax Info" option to view your CSN.

First Time Filers

If you are filing an SBT annual return for the first time, you will not have a CSN and will not be able to e-file using the SBT Direct Program. A CSN will be assigned to your account if your business is registered to do business in Michigan. You can access your CSN through the "Check My Business Tax Info" option at www.michigan.gov/bustax or www.michigan.gov/taxes.

If as a first-time filer your business is not registered, you need to register in Michigan to be eligible to receive a CSN. You can register for Michigan business taxes online. Registered taxpayers filing a second Michigan SBT return can find their CSN through the "Check My Business Tax Info" option at www.michigan.gov/bustax or www.michigan.gov/taxes. The CSN should be available in January of the following calendar year.

For example: The 2007 SBT return is due and received on April 30, 2008. The CSN should be available using the "Check My Business Tax Info" option in January 2009.

Learn more about the SBT e-file program here.