Rosh Chodesh Teves Yaaleh Viyavo When Davening
If you forgot to say Yaaleh Viyavo during Maariv and remembered after saying Hashem’s name at the end of the berachah, do not go back to repeat it.
If you forgot to say Yaaleh Viyavo during Shacharis or Minchah and remembered after saying Hashem’s name at the end of the berachah, finish the berachah and say it before Modim.
If you already began saying Modim, go back to Retzei. If you already said the second Yihiyu leratzon at the end of Shemoneh Esrei, go back to the beginning of Shemoneh Esrei.
If you forgot to say Yaaleh Viyavo during Shacharis and only remembered after davening Musaf, do not repeat the Shemoneh Esrei of Shacharis.
If you forgot to say Yaaleh Viyavo during Minchah and only remembered at night, daven Maariv twice, once for Maariv and the second time as a voluntary tefillah. However, since it is no longer Rosh Chodesh, do not say Yaaleh Viyavo during either Shemoneh Esrei.
All the above also applies if you are unsure whether you have said Yaaleh Viyavo.
