If someone accepts shabbos and makes kiddush after plag hamincha all year round, when friday is erev rosh codash should he make yaleh veyovah at benching or not?
Authorities dispute whether when davening early on Shabbos night one says ya’aleh veyavo in Ma’ariv. The reason why some write it shouldn’t be recited is that there is no tosefes for Rosh Chodesh (Magen Avraham), and therefore ya’aleh vehavo can’t be said (Eretz Tzvi 26). Others write that ya’aleh veyavo can still be recited, as the night prayer for Rosh Chodesh can be davened early (She’elas Yaavatz, Orach Chaim 2:2), and this is the principle halachah for davening.
However, because there is no tosefes rosh chodesh, if benching early one would not recite ya’aleh veyavo. For somebody making kiddush early, it is preferable to ensure that one eats some bread after nightfall, and then benching would be recited with ya’aleh veyavo.