When do girls who have not yet menstruated become religiously accountable?

Religious accountability begins with reaching puberty. Girls are considered to have reached puberty when they experience menstruation. If a girl has not reached puberty by the age of 15, she is deemed legally pubescent and accountable from the date she completes her 15th year. (Mevsılî, el-İhtiyâr, 2/95; Tahtâvî, Hâşiye, 108; İbn Âbidîn, Reddü’l-muhtâr, 1/408)

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu