We closed our business because it was failing where it was located at. We were month to month and decided to close instead of falling deeper into financial death. When we originally leased the building we paid the first months rent and a deposit in the same amount. When we decided to leave it was four days after the month began. Should we have to pay and entire months rent and if so why not keep the initial deposit. Do we just forfeit our deposit? Or should we be prorated the four days for rent and the difference be refunded to us?

You have not said where you are, but in general, for commercial as well as residential rentals, the rules are that deposits cannot be credited toward the last month's rent, and if you occupy the premises for a part of the month you are liable for the full month. Also, since you apparently failed to give advance notice, you would be liable for at least the month, for that reason as well.

I am assuming you didn't have a written lease. If there was one, the terms of the lease would control.