Embodiments relate to tagging in a MCU. An aspect includes assigning a command tag to a command by a tag allocation logic of the MCU. Another aspect includes sending the command and the command tag on a plurality of channels that are in communication with the MCU. Another aspect includes receiving a response tag comprising one of a data tag and a done tag corresponding to the command tag from each of the plurality of channels. Another aspect includes, based on receiving a data tag from each of the plurality of channels, determining that read data corresponding to the command is available.