Only servicemen who take direct part in hostilities and have received an extract confirming the payment of additional remuneration are exempted from paying the military tax.
https://www.kmu.gov.ua/npas/pro-vnesennia-zmin-do-postanovy-kabinetu-ministriv-a244 - Resolution of the CMU "On Amending the Resolution of the Cabinet of Ministers of Ukraine of December 30, 2015 No. 1161"