A "combat" summons (mobilization order) can be handed over to a person liable for military service only by the Territorial Recruitment and Social Support Centers (TCC SP) after he has passed the military medical commission, and provided that he is declared fit for military service.
This was stated in a comment to the TSN.ua website by lawyer Maryna Bekalo.
In total, there are four types of summonses: for clarifying data, for a medical commission, for a mobilization order, and for conscription. During martial law and mobilization in Ukraine, authorized persons can serve three types of summonses, in addition to the last one.
Recall that the spokeswoman of the Cherkasy TCC, Alina Kryvosheya, told who else can serve summonses, except for representatives of the military registration and enlistment office.