After the exchange is complete, the closing agent is supposed to give you copies of all the documents used in the transaction. When you have closed on the identified property or your 180-day period is over, your exchange ends. We will return any unused proceeds. Ideally you should try to use the entire proceed for your 1031 property exchange as any remaining balance is taxable on their full amount.
While filing your taxes you need to report the exchange through: IRS form 8824 “Like Kind Exchanges”
