Bar Mitzva for someone who was born on chol a-moed

Dear Rabbi, we have the following question. Our son was born on the eighteenth of Tishrei. This year he’s going to become bar-mitzva (13). We’d like to know when he should be called up for Torah reading, and when should he start putting on his tefillin (phylacteries). Maybe, because we can’t do it on the actual date that he was born, we should do it the week after the holidays, and then he’ll begin putting on his tefillin? Thank you very much and a big mazal tov

Starting on the day of the bar mitzva, i.e., from the eighteenth of Tishrei 5783, your son becomes obligated in keeping commandments. From that day onward, he has to keep all the commandments of the Torah. This includes putting on tefillin every day. Most communities have the custom of not putting on tefillin on chol ha-moed (intermediary days of the holidays). And therefore, from the day the holiday is over, that is from Tuesday, 23 of Tishrey, and outside Eretz Yisroel, from Wednesday, 24 of Tishrei, your son must put on tefillin every morning. This obligation, as well as the obligation to keep all other commandments, has nothing to do with whether your son has been called for a Torah reading, and whether you celebrated the event.

As far as the Torah reading is concerned, you son can be called for a Torah reading on any day that is convenient for you. It’s better to do it as close to the actual date of the bar-mitzva as possible.

Moreover, your son can be called for a Torah reading during the holiday itself. It can be done without making a large celebration anywhere you want, in your synagogue, or at the Wailing Wall, or anywhere else. On that day, you can make a small reception for the family. Afterwards, he can be called for a Torah reading again after the holiday is over, on any day that is most convenient for you. Then you can hold a big banquet in honor of this momentous event.

Shulchan Oruch, section Orach Chaim, ch. 55, § 9