(a) On receipt of medical bills submitted in accordance with §133.10 of this chapter (relating to Required Billing Forms/Formats), an insurance carrier must evaluate each medical bill for completeness as defined in §133.2 of this chapter (relating to Definitions).(1) Insurance carriers must not return medical bills that are complete, unless the bill is a duplicate bill.(2) Within 30 days after the day it receives a medical bill that is not complete as defined in §133.2 of this chapter, an insurance carrier must:(A) complete the bill by adding missing information already known to the insurance carrier, except for the following:(i) dates of service;(ii) procedure or modifier codes;(iii) number of units; and(iv) charges; or(B) return the bill to the sender, in accordance with subsection (c) of this section.(3) The insurance carrier may contact the sender to get the information necessary to make the bill complete, including the information specified in paragraph (2)(A)(i) - (iv) of this subsection. If the insurance carrier gets the missing information and completes the bill, the insurance carrier must document the name and telephone number of the person who supplied the information.(b) An insurance carrier must not return a medical bill except as provided in subsection (a) of this section. When returning a medical bill, the insurance carrier must include a document identifying the reasons for returning the bill. The reasons related to the procedure or modifier codes must identify the reasons by line item.(c) The proper return of an incomplete medical bill in accordance with this section fulfills the insurance carrier's obligations with regard to the incomplete bill.(d) An insurance carrier must not combine bills submitted in separate envelopes as a single bill or separate single bills spanning several pages submitted in a single envelope.