"As on 16 May" vs. "as of 16 May" — which is correct?

I updated a cost sheet and I want to specify that it's a newly updated cost sheet. For this situation, which one is correct?

cost sheet as on/of 16 May

Before specifying a date, which will come first, on or of?

They are both correct but mean different things in different situations. As of May 16 indicates the start of something; from that time on, while as on May 16 is completely different. As in as on May 16 means such as; like and is used for comparison.

As of May 16, 2012 cigarettes are banned in this country.

As on May 16, he again failed to attend the conference.

Back to your specific example. In your case as of makes more sense because you want to say that the sheet covers cost from May 16 on.

"as of" is the same as "as from": used to show the time/date from which something starts, e.g. As of/from Monday, we shall give all of you winning bonuses.