A method for reporting a power headroom for multiple cells in a wireless communication system, the method performed by a wireless device and comprising: receiving first downlink control information, DCI, for scheduling a physical uplink shared channel, PUSCH, transmission in a first time slot on a first bandwidth part, BWP, of a first serving cell; receiving second DCI for scheduling a PUSCH transmission in a second time slot on a second BWP of a second serving cell; receiving third DCI for scheduling a PUSCH transmission for a third serving cell; computing a first power headroom, PH, for the PUSCH transmission in the first time slot on the first BWP of the first serving cell; based on the first time slot overlapping at least in part with each of a plurality of time slots on the second BWP of the second serving cell, wherein the first BWP of the first serving cell has a first subcarrier spacing, SCS, which is smaller than a second SCS of the second BWP of the second serving cell such that a duration of each time slot on the first BWP is longer than a duration of each time slot on the second BWP: computing a second PH for the PUSCH transmission in the second time slot on the second BWP of the second serving cell, wherein the second time slot is an initial time slot, among the plurality of time slots, which fully overlaps in time with the first time slot; and reporting the first PH and the second PH, wherein the first DCI includes a transmit power command, TPC, to be applied to the PUSCH transmission in the first time slot on the first BWP of the first serving cell, and a delay field related to delay between a time slot in which the first DCI was received and the first time slot in which the PUSCH transmission is performed on the first BWP of the first serving cell, and wherein the first PH for the PUSCH transmission for the first serving cell is computed without considering the PUSCH transmission for the third serving cell based on the PUSCH transmission for the first serving cell overlapping in time with the PUSCH transmission for the third serving cell, and the third DCI being received after the first DCI. receiving first downlink control information, DCI, for scheduling a physical uplink shared channel, PUSCH, transmission in a first time slot on a first bandwidth part, BWP, of a first serving cell; receiving second DCI for scheduling a PUSCH transmission in a second time slot on a second BWP of a second serving cell; receiving third DCI for scheduling a PUSCH transmission for a third serving cell; computing a first power headroom, PH, for the PUSCH transmission in the first time slot on the first BWP of the first serving cell; based on the first time slot overlapping at least in part with each of a plurality of time slots on the second BWP of the second serving cell, wherein the first BWP of the first serving cell has a first subcarrier spacing, SCS, which is smaller than a second SCS of the second BWP of the second serving cell such that a duration of each time slot on the first BWP is longer than a duration of each time slot on the second BWP: computing a second PH for the PUSCH transmission in the second time slot on the second BWP of the second serving cell, wherein the second time slot is an initial time slot, among the plurality of time slots, which fully overlaps in time with the first time slot; and reporting the first PH and the second PH, wherein the first DCI includes a transmit power command, TPC, to be applied to the PUSCH transmission in the first time slot on the first BWP of the first serving cell, and a delay field related to delay between a time slot in which the first DCI was received and the first time slot in which the PUSCH transmission is performed on the first BWP of the first serving cell, and wherein the first PH for the PUSCH transmission for the first serving cell is computed without considering the PUSCH transmission for the third serving cell based on the PUSCH transmission for the first serving cell overlapping in time with the PUSCH transmission for the third serving cell, and the third DCI being received after the first DCI. computing a second PH for the PUSCH transmission in the second time slot on the second BWP of the second serving cell, wherein the second time slot is an initial time slot, among the plurality of time slots, which fully overlaps in time with the first time slot; and reporting the first PH and the second PH, wherein the first DCI includes a transmit power command, TPC, to be applied to the PUSCH transmission in the first time slot on the first BWP of the first serving cell, and a delay field related to delay between a time slot in which the first DCI was received and the first time slot in which the PUSCH transmission is performed on the first BWP of the first serving cell, and wherein the first PH for the PUSCH transmission for the first serving cell is computed without considering the PUSCH transmission for the third serving cell based on the PUSCH transmission for the first serving cell overlapping in time with the PUSCH transmission for the third serving cell, and the third DCI being received after the first DCI.