We have a business customer that opened an account with an 02# instead of an 04#. How do I determine if this is valid?

The fact it is an #02, instead of an 04# should not alarm you. Different areas of the country have different starting numbers for TIN's, similiar to soc. sec numbers. 02's used to be( and may still be) used a lot in Vt for TIN's. I know that recently they have also been used in MA.