Should Co have a period?
Simply so, should Ave have a period?
Occasional Moderator. In BE, abbreviations generally donot require punctuation. The middle path is, as has beensuggested, to include a full stop (period) if theabbreviation does not include first and last letters - So St andAve have no punctuation just because they areabbreviations.
Simply so, do you put periods in acronyms?
There is no strict rule on using periods (fullstops) in acronyms. You don't see N.A.S.A, B.B.C, orN.A.T.O often because they are so popular/familiar. However,you might have to put the periods if anacronym you use is not that familiar withreaders.
This one is simple enough: never double upperiods. If a statement ends with “etc.”the period in the abbreviation does doubleduty, serving as the full stop to end the sentence. If,however, you need another mark of punctuation after anabbreviation, you can put it after theperiod.