FAQ How do I qualify for “In County” rates for my periodical mailings? The first step is to format the FIPS field. This is a 5 character field that contains the Federal Information Processing Standard and is populated by MAILERS+4 during Address Check. The first 2 digits of this field is the state code and the last 3 digits is the county code. Then select the “Use In-County” check box to receive the In-County discount for mail delivered within your county of mailing. The FIPS code of qualifying records must match your post office FIPS code.