Amida Errors: Ya'aleh V'Yavo

Situation You forgot to say ya'aleh v'yavo in the 15th amida paragraph (retzei) when required on Rosh Chodesh day or chol ha'moed.
Status Not Yet Ready To Take 3 Steps Back
WHAT TO DO As soon as you realize that you forgot, return to the beginning of retzei and continue.
status Ready To Take 3 Steps Back
WHAT TO DOYou must repeat the entire amida from the beginning.
NOTE If you forgot to add ya'aleh v'yavo on Rosh Chodesh night, even if you just finished retzei when you realized that you had omitted ya'aleh v'yavo, do not repeat the amida.