Do I have to spend everything in my 1031 account?

You are not required to use all of your funds. However, any unused amount will be treated as cash boot and be subject to capital gains taxes, along with any applicable recaptured depreciation. For example, if the property you sold (Relinquished) yields $500,000.00, and the property you bought (Acquired) costs $400,000.00, the remaining $100,000.00 would be considered as cash boot and subject to taxation.