1099-g box 10b is blank but state taxes were withheld for state of michigan

Since you had state taxes withheld from your unemployment, but there is not a state ID number on your form, then use the Federal ID number in box 10b.

If you did not have any state taxes withheld, then leave all the boxes blank (boxes 10a, 10b, and 11).  This includes the dropdown box for the state name.

If anything is entered in box 10a, 10b, or 11, then all of them must be filled in to avoid an error condition causing you to review the entry.  

Annette - the Michigan tax ID for form 1099 G substitute has a different number than the federal ID number.   Is there a difference between the 1099 G and substitute form 1099 G?   I was able to locate online for substitute 1099 G the number 38-600134 which is not the Payers TIN which is 38-2538297.  How do I know which one to use?

You should use the Michigan tax ID that is on the Form 1099-G substitute that you have.