Giving tzedakah on erev Rosh Hashana is considered a great mitzvah.  In fact, as a result of Jews giving tzedakah, the Heavenly Gates of Mercy are opened wide.  For in the same measure that we take pity on the poor, Hashem takes pity on us. ~ Ohr Hachayim as quoted by R’ Dovid Meisels

Shana Tova!