According to the TR3, it would appear as if the 2400 REF Referral Number (REF01=9F), is allowed to be present, even when the 2300 REF Referral Number (REF01=9F) is not present.
If the 2300 REF Referral number refers to the "entire claim" and the 2400 REF REferral number refers to a specific service line, then the 2400 REF could possibly be there without the 2300 REF. This woudl be "different" from the 2300 REF since there is no 2300 REF.
Question: Should a claim reject if there a 2400 REF01=9F and NO 2300 REF01=9F?
The Situational Rule for usage of the 2300 REF Referral Number reads:
“Required when a referral number is assigned by the payer or Utilization Management Organization (UMO) AND a referral is involved. If not required by this implementation guide, do not send.” The Situational Rule for usage of the 2400 REF Referral Number reads: “Required when this service line involved a referral number that is different than the number reported at the claim level (Loop-ID 2300). If not required by this implementation guide, do not send.”
If a Referral Number is assigned and a referral is involved it must be sent in the 2300 REF Referral Number segment. If this condition is not met and the 2300 REF Referral Number is not sent, then the 2400 REF Referral Number must not be sent because the Referral Number at the line level cannot be different than the 2300 REF Referral Number since none exists.
ASC X12 does not govern the receiver's actions when receiving a transaction that is not compliant with the specified implementation guide. Section 2.2.1.1 in TR3s published by the ASC X12 Insurance Subcommittee makes this clear with the statement "The receiver will handle non-compliant transactions based on its business process and any applicable regulations."