Your question can be interpreted and thus answered in several different ways.

Microsoft do not -- at least so far -- make Office products for the iPad. Several third-party companies and Apple themselves make "office-like" products whose files are generally MS Office-compatible and which can be easily transferred back to a computer.

IMO, the most complete current solution is to buy the iWork suite for the Mac and the iWork apps for the iPad, using the iCloud for Documents solution to easily make your files available from any internet-connected computer. I have not tried every possible alternative solution out there, however.

I did notice the other day a company called OnLive offering that works in a different way but might suit your needs:

OnLive releases OnLive Desktop for iPad | MacNN

There's also a company called Good Technology that you may want to check out as well.