Do I have to pay taxes on insurance paid on apartment building due to fire We r corporation?

Maybe.. The best way to describe the situation is to think of it as a sale of the property. You don't have to pay taxes on insurance proceeds up to the amount of your tax basis on the property. You will have to pay taxes on any payments above your tax basis. If you receive more than your basis you pay tax on the gain. This is assuming the property is a total loss. If it was repaired, then your basis would transfer to the repaired property, no loss, no gain.