A 1031 exchange lets you sell an investment property and roll the full proceeds into another one, deferring capital-gains tax and depreciation recapture that would otherwise take a large bite at closing. It's the mechanism behind "trading up" a portfolio for decades without paying tax along the way. The rules are strict and the deadlines unforgiving — this is a transaction you run WITH a qualified intermediary and a CPA, not after reading anything, including this.
The non-negotiable mechanics
You never touch the money: a qualified intermediary (QI) must hold the sale proceeds — take receipt of even a dollar and the exchange fails. Two clocks start at your sale's closing: 45 days to identify replacement property in writing (commonly up to three candidates), and 180 days to close on one. Both properties must be held for investment or business use — not your home, not a flip. To defer ALL the tax, buy equal or greater value AND reinvest all equity; buy cheaper or pocket cash ("boot") and that portion is taxable.
What deferral is worth
Selling a long-held rental can trigger 20–30%+ of the gain in combined federal capital gains, depreciation recapture (up to 25%), state tax, and possibly net investment income tax. A 1031 keeps that money compounding in the next property. Serial exchangers defer for decades; under current law, heirs may receive a stepped-up basis that erases the deferred gain entirely — the "swap till you drop" strategy your CPA can evaluate.
Worked example
You sell a fourplex for $600,000 that you bought for $350,000 and depreciated by $90,000. Without an exchange, roughly $65,000–$90,000 of combined tax is due at closing (bracket- and state-dependent). With a 1031, the full $600,000 of value moves into a $700,000 eight-unit building (new loan covers the difference). The deferred tax stays invested — at the new property's yield, that's several thousand dollars a year of return earned on the government's money.
When this rule of thumb breaks
The 45-day clock is the killer: identifying quality replacement property in a hot market in six weeks pressures people into overpaying — a bad building bought to dodge tax is usually a worse outcome than paying the tax. Exchanging into lower-basis property keeps your depreciation small. Related- party rules, partnership-interest complications, and reverse exchanges (buy first, sell second) each have their own traps. And if your gain is modest or you have offsetting losses, the QI fees and constraints may simply not be worth it. Model both paths with a CPA before listing.