Answer: In 5G we have Registration Area Update (RAU) instead of Tracking area Update (TAU). A Registration area is a list of tracking areas that are assigned to UE by 5G Network. This is especially useful in the high mobility scenarios where assigning a tracking area list (Registration Area) to UE reduces the signalling on the network as UE only informs the 5G network about its position when it moves from one Registration Area to another.
However, there is another procedure called RAN based Notification Area Update (RNAU) that should not be confused with RAU. RNAU is only used when the UE is in RRC_Inactive state. And RNAU procedure is used to save UE battery and is local to the RAN.