Hoshana Rabbah
There is a Kabbalistic belief that, though judgment is made absolute on Yom Kippur, it is not registered until the seventh day of Sukkot, known as Hoshana Rabbah. The service for this day therefore contains some reminiscences of those for the High Holy Days, and it is treated as a last opportunity to repent of sins that may have been missed on Yom Kippur.
Read more about this topic: High Holidays