Gigi’s question: “I would like to know the difference between ‘as at’ and ‘as of.’ ”
BizWritingTip response: As of is used to indicate a time or date at which something begins or ends. Although precise, it sounds rather formal.
The project was terminated as of January 1. (Less formal: The project has been terminated since January 1.)
You will be able to access the system as of 3 p.m. (Less formal: You should be able to access the system after 3 p.m.)
I checked a number of North American dictionaries but could not find a mention of “as at.” However, a friend in the accounting industry says it is used when referring to a snapshot of a position at a particular time in a financial document, such as a balance sheet. For example, “As at January 30, the organization is exceeding its sales projections for the quarter.”