надбавка - feminin noun

	singular	plural
Nominative	надбавка	надбавки
Genitive	надбавки	надбавок
Dative	надбавке	надбавкам
Accusative	надбавку	надбавки
Instrumental	надбавкой / надбавкою	надбавками
Prepositional	надбавке	надбавках