Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos) By the Chofetz Chaim

This book lists the Torah mitzvos that can be observed today

Second Section – the Negative Commandments

119. It is a negative commandment “do not have relations with the daughter of one’s son” and it is a negative commandment “do not have relations with the daughter of one’s daughter”

As it states in Vayikra (Leviticus) 18:10, “you shall not uncover the nakedness of your son’s daughter or your daughter’s daughter.” The punishment for this transgression is death by burning. If it is committed with intent but no witnesses, the person receives spiritual excommunication. If done by error, a sin-offering is required. According to the Rabbinic law of Shinus, in addition to the daughter of his son: the daughter of his son’s daughter and the daughter of his son’s son, but these do not extend to other generations. According to the Rabbinic law of Shinus, in addition to the daughter of his daughter: the daughter of his daughter’s daughter and the daughter of his daughter’s son, but these do not extend to other generations.

This applies in all places and at all times.