Sorry I anwsered before noticing there where already plenty anwsers.
So this anwser can be ignored.

Year = DATEPART(YEAR, DATEADD(MONTH, -1, GETDATE()))
AND Month = DATEPART(MONTH, DATEADD(MONTH, -1, GETDATE()))


ZZartin did give the anwser to the question: How do I get the previous month.

Januar will give december of the previous year.
Februar will give januar of the SAME year.
March ......    etc.

The question with the 'LAST' month is a bit ambiguous.
I think that what you wanted is deliverd by ZZartin, if not restate the question.

Ben
(Sorry to 'break' in on your anwser ZZartin,but seeing the other posts, I think this needed some extra explanation).