is alimony decutable when in same home

It depends. If at the time of the payment you are residing in the same home (separate quarters are not relevant) AND you are legally separated or divorced under a decree of divorce or separate maintenance, you have one month to vacate from the date of the payment. Otherwise, it is not deductible alimony. If at the time of the payment you are legally obligated to make the payment under a decree that is not a decree of divorce or separate maintenance or a written agreement, then where you live is not relevant. The payment would be deductible alimony.

The above answer assumes that all of the other requirements for what is alimony are present.

Pub. 504 says:

Thanks Alan, dumb question (although I will be out in 30 days) ... how can the IRS check one way or other?

NSA spy satellites.