Halacha requires lighting candles each week before the onset of Shabbat, and before the onset of Yom Tob. Before lighting the Shabbat candles one recites the Beracha, "Le’hadlik Ner Shel Shabbat," and before the lighting for Yom Tob one recites, "Le’hadlik Ner Shel Yom Tob." This is codified by the Shulhan Aruch (Orah Haim 263).
In this context, the Shulhan Aruch observes that some people have the custom to also light candles for Yom Kippur, though they do not recite a Beracha on this lighting.
In truth, the issue of candle lighting for Yom Kippur is subject to a debate among the Rishonim. The Rosh (Rabbenu Asher Ben Yehiel, Germany-Spain, 1250-1327) maintained that candles should be lit in the home on Yom Kippur as a safeguard against marital relations, which are forbidden on Yom Kippur. Since marital relations should take place only in the dark, having lights in the home on Yom Kippur helps ensure that husbands and wives will not violate this prohibition. The Mordechi (Rav Mordechai Ben Hillel, 1250-1298), however, maintained that to the contrary, if lights are lit in the home, a husband may look at his wife and desire relations, and so it is preferable not to have lights in the home on Yom Kippur.
In contradistinction to his aforementioned comments, the Shulhan Aruch later, in discussing the laws of Yom Kippur (610), mentions only the view of the Rosh, that candles should be lit for Yom Kippur, adding that according to this view, a Beracha is recited at the time of lighting ("Le’hadlik Ner Shel Yom Ha’kippurim"). It thus appears that he accepted the Rosh’s ruling, and maintained that one should light candles for Yom Kippur and should even recite a Beracha over the lighting. The Rama (Rav Moshe Isserles of Cracow, 1525-1572) writes that this was the custom among Ashkenazic communities, and this is also the position taken by many Ashkenazic authorities (Rav Sheneur Zalman of Liadi, Peri Megadim, Mateh Efrayim and Hayeh Adam). Numerous Sephardic authorities accept this view, as well, including the Ben Ish Hai and Kaf Ha’haim.
Others, however, disagree, and maintain that in light of the different views that exist among the Rishonim, we must apply the principle of "Safek Berachot Le’hakel" – we do not recite a Beracha when there is some uncertainty as to whether it is warranted. Therefore, in their view, a Beracha should not be recited over the Yom Kippur candle lighting. This is the view of Rav Haim Palachi (in Ruah Haim), the Peri Hadash, the Erech Ha’shulhan, and others.
As for the final Halacha, Hacham Ovadia Yosef ruled that in communities with an established custom, we do not apply the principle of "Safek Berachot Le’hakel." Therefore, communities that have a custom to recite a Beracha over the Yom Kippur candle lighting should follow this custom. This is also the ruling of Hacham Bension Abba Shaul (Israel, 1923-1998).
The accepted custom in Halab (Aleppo, Syria) was to either not light candles for Yom Kippur, or to light candles without a Beracha. This is documented in the book Derech Eretz, and in the Kol Yaakob weekday Siddur, too, it says that the custom among the Jews of Halab was not to recite a Beracha over the Yom Kippur candle lighting. The exception to this rule, however, is when Yom Kippur falls on Shabbat, in which case candles must be lit before the onset of Yom Kippur because of Shabbat. The custom in Aleppo was to recite at the time of candle lighting in this case the Beracha, "Le’hadlik Ner Shel Shabbat Ve’Yom Ha’kippurim." Hacham Eliyahu Hamoui ruled that even in this case no Beracha should be recited, but the consensus view is that according to the custom of Halab, a Beracha is recited over the Yom Kippur candle lighting when Yom Kippur falls on Shabbat.
It should be noted that women who attend the synagogue service on the night of Yom Kippur recite the Beracha of "She’he’hiyanu" together with the congregation in the synagogue. If a woman does not attend the service in the synagogue, she must still recite the Beracha, as this Beracha is recited over the occasion of Yom Kippur, not as part of the Kal Nidreh service.
Summary: It is customary in most communities to light candles before the onset of Yom Kippur and to recite a Beracha over the candle lighting, but the custom in Halab (Aleppo) was not to recite a Beracha over this candle lighting, except when Yom Kippur falls on Shabbat.
