Regex for US Federal Tax ID (EIN)

Question

In the pattern attribute of an input tag, I am using the following regular expression for validation of the US Federal Tax ID field.

pattern=\"^([07][1-7]|1[0-6]         


        

Answer 1

I have written a regex which satisfy the requirements.

pattern="^((?!11-1111111)(?!22-2222222)(?!33-3333333)(?!44-4444444)(?!55-5555555)(?!66-6666666)(?!77-7777777)(?!88-8888888)(?!99-9999999)(?!12-3456789)(?!00-[0-9]{7})([0-9]{2}-[0-9]{7}))*$"

Though it is not an efficient one. Anyone has more efficient regex?