Radio frequency identification (RFID) is an automatic identification technology which identifies physical objects individually according to their unique identifiers (ID) recorded in each RFID tag. Many business processes require the integrity verification of a group of objects in addition to individual object identification. This paper proposes “group coding” of RFID tags with which we can verify the integrity of groups of objects by writing parity check data to the memory of RFID tags. It was revealed by simulations and experiments that we could determine the number of missing RFID tags up to 10 with accuracy over 99% when we write 96 bits of the checksum data to 20 RFID tags. The whole duration of group decoding measured in the experiment was approximately 2 to 3 s. The time to compute group encoding and decoding was in the order of several milliseconds and thus negligible. The RFID inventory accounts for the majority of the duration. Note to Practitioners-Current RFID features fast identification of many physical objects. However, the integrity check of a group of objects is usually done by looking up a packaging list or a shipment list in EDI, which requires a network connection. Our proposed “group coding” of RFID tags can perform the group integrity check without a network connection. In addition, when the integrity of the group is infringed, the group coding can determine the number of RFID tags missing from the group. These features of group coding can reduce the cost of looking up shipment lists and locate missing RFID tags. The accuracy of the determination is controlled by adjusting the size of data written in each RFID tag. Adopters of group coding can select the optimal performance of group coding from the requirements of the accuracy and constraints like memory consumption of RFID tags.