What is 1031 Exchange?

Legal Definition
An exchange, i.e. sale and reinvestment of the proceeds therefrom, of business or investment property for like-kind business or investment property, which allows a seller to defer payment of capital gains taxes.
Illustrative caselaw
See, e.g. Teruya Bros., Ltd. v. C.I.R., 580 F.3d 1038 (9th Cir. 2009)
See also