After Shaḥarit, two Torah scrolls are removed from the ark. From the first scroll we read the description of the Kohen Gadol’s avoda on Yom Kippur, which is found in the portion of Aḥarei Mot (Vayikra 15). Six people are called up to the Torah. The number of people called up to the Torah for an aliya changes in accordance with the holiness of the day. On Yom Tov, when melakha is forbidden but food preparation is permitted, five people are called up. On Yom Kippur, when all melakha is prohibited, six people are called up. On Shabbat, when all melakha is prohibited and the punishment for desecration is greater, seven people are called up. If Yom Kippur is on Shabbat, seven people are called up (Megilla 21a, 22b; SA 621:1).
The maftir is read from the second Torah scroll. It is taken from the portion of Pinḥas and deals with the additional (“musaf”) sacrifices offered on Yom Kippur (Bamidbar 29:7-11). The haftara is from Yeshayahu (57:14-58:14), which is an appropriate choice because the prophet exhorts the people to repent, and the verses mention resting on Shabbat and Yom Kippur.
At Minḥa there are three aliyot, and we read a section of the Torah dealing with prohibited sexual relations (Vayikra 18). It is meant to inspire the people to repent for and refrain from these extremely tempting but very serious transgressions that impair our holiness. The haftara is the Book of Yona, which teaches us about divine providence, from which no one can hide. It also teaches us about the great power of repentance, which is effective even when incomplete, as God does not wish to punish sinners (Megilla 31a; SA 621:1).
On Yom Kippur, it is customary to pledge money to the poor and to those dedicated to Torah study, in order to elevate the souls of parents and family members who have passed away. For the dead also achieve atonement on Yom Kippur when charity is given on their behalf (Mordekhai; SA and Rema 622:4). This is why the day is called Yom Ha-kippurim (in the plural), as it atones for both the living and the dead. But haven’t those who have died already been judged? How can charity help them? When their children and family members are inspired to donate money and do good deeds in their memory, it shows that the departed souls continue to have a positive influence on the world. Therefore, they earn the right to be judged again in the heavenly court, taking into account the additional merits they have accrued.
. Another answer is that in the heavenly court it is said that if the deceased were still alive, they, too, would give charity. Ashkenazim recite Yizkor, the memorial prayer, on Yom Kippur, Pesaḥ, Sukkot, and Shavu’ot. The prayer is meant to be recited with the congregation but may also be recited by an individual praying alone (Gesher Ha-ḥayim, vol. 1, 32:1). Generally, before the prayer is recited, the gabbai announces “Yizkor”, and those whose parents are both still alive leave the synagogue temporarily. Several reasons are given for this practice. The primary one is that it is unpleasant to have some members of the congregation recite the prayers while others stand silent. Additionally, there are those who are concerned about bad omens. There is a common custom that the first time one is mourning a parent, he does not recite Yizkor during the year of mourning. This is out of concern that if he did recite Yizkor, his powerful grief might make it impossible for him to fulfill the mitzva of rejoicing on the holiday. (See Peninei Halakha: Festivals 2:8; Piskei Teshuvot 621:7.)