When incoming transaction set has following ST segment content:
ST*270*0001
is it appropriate to respond to such transaction with 999 (version 005010X231A1) that has AK2 segment as:
*004010A279A1
Value "004010A279A1" is invalid for incoming 270 transaction. Should it be passed in AK203 back or should such transaction be rejected at the functional group level (with only AK2/AK9 segment in 999) ?
Yes, it is appropriate to respond with a 999 that references the values in AK203. AK203 contains whatever the sender placed in ST03, provided the content of ST03 contains valid X12 approved Character sets. If the receiver does not recognize 004010A279A1, the transaction set can be rejected with a reason code of: I6 Implementation Convention Not Supported, or 19 Invalid Transaction Set Implementation Convention Reference. The receiver may exercise discretion regarding acceptance or rejection of the transaction set based on this type of error. It is not correct to reject the functional group based on the error of the ST03 as described in the example presented.