"Check the box" confuses me

[LCP]

Can an existing partnership choose to be treated as an s-corp or do the check the box rules only apply to new entities and the first tax return that is filed?

[Lion]

Time of election

They apply to the time of the election or up to 3.5 months prior. So, if an existing entity that has been filing tax returns decides it wants to be taxed as an S corp, for instance, beginning with the 2010 tax year, it could "check the box" ahead of time. I don't think any of the late election procedures work if the business has already been filing returns as one type of entity and changes its mind. Well, I did blame the lawyer for not filing the election once for an LLC that told their lawyer to make them an S, and a late election was granted for what had been taxed as a partnership in all the prior years.

[LCP]

Looks like there is a 75 day rule now so that an electin on 3/15/10 would have worked for 1/1/10.

I could be wrong on that though.

Is there any reason why an election made now couldn't go into effect January 15, 2010 so that a short year 1065 thru 1/15 could be filed and the entity be an S-Corp from that point forward?