Here's the official patron saint of accounting, Saint Matthew:
"The patron saint of accountants, bankers, bookkeepers, security guards and tax collectors is Saint Matthew of Apostle fame, and he also was the author of one of the Gospels. Before becoming an Apostle, however, he started out as a Jewish tax collector at Capernaum. Little is known about him, outside the seven references he has in the Gospels. In medieval art, Saint Matthew is represented under the symbol of a winged man, carrying in his hand a lance as a characteristic emblem - his artistic calling card if you will. He is one of the originals in the pantheon of patron saints."
Okay, that's the official line. My nominee for the patron saint of accounting would be