Current HARQ procedures for grant-based uplink transmissions may not be suitable for implementations in which a UE can simultaneously transmit multiple transport blocks (TBs) to a base station. However, in some scenarios, such as in some grant-free uplink transmission schemes, a UE may simultaneously transmit multiple TBs. Systems and methods are disclosed herein for performing HARQ for situations in which a UE simultaneously transmits multiple TBs to a base station. By using the systems and methods described herein, HARQ may therefore be performed in such situations.