When To Report 
Gains and Losses(p12)

If you receive an insurance or other reimbursement that is more than your adjusted basis in the destroyed or stolen property, you have a gain from the casualty or theft. You must include this gain in your income in the year you receive the reimbursement, unless you choose to postpone reporting the gain as explained earlier.

Generally, you can deduct a casualty loss that is not reimbursable only in the tax year in which the casualty occurred. This is true even if you do not repair or replace the damaged property until a later year. (However, see Disaster Area Losses, later, for an exception.)

You can deduct theft losses that are not reimbursable only in the year you discover your property was stolen.

If you are not sure whether part of your casualty or theft loss will be reimbursed, do not deduct that part until the tax year when you become reasonably certain that it will not be reimbursed. See the Form 4684 instructions if you are deducting a loss of personal use property from a disaster declared a federal disaster in tax years beginning after 2007 that occurred before 2010.

If your loss is a loss on deposits at an insolvent or bankrupt financial institution, see Loss on Deposits, earlier.

If you lease property from someone else, you can deduct a loss on the property in the year your liability for the loss is fixed. This is true even if the loss occurred or the liability was paid in a different year. You are not entitled to a deduction until your liability under the lease can be determined with reasonable accuracy. Your liability can be determined when a claim for recovery is settled, adjudicated, or abandoned.