Kiplinger Calculates How Treasury Inflation Indexing Could Save Retirees Tens of Thousands on a $500,000 Portfolio

A proposal would allow the Treasury Department to index the cost basis of capital gains to inflation through regulation rather than requiring new legislation. For a taxable portfolio liquidated after long holding periods, indexing would replace the original purchase price with a basis increased by cumulative inflation, reducing the taxable gain. Under current law, nominal gains are taxed at long-term capital gains rates, with higher-income sellers also facing the net investment income tax. With an assumed 3% average annual CPI and a position bought around 2015, inflation over roughly 11 years would shrink the taxable gain substantially. Inflation continues to create “phantom” gains while assets remain in taxable accounts, and the tax savings would scale with holding period and gain size.

"Kiplinger has reported that the Treasury Department is studying whether it can index the cost basis of capital gains to inflation through regulation, without an act of Congress. For a retiree liquidating a long-held taxable account, the dollar impact is large enough to change retirement planning. Model the case the Kiplinger piece centers on: a $500,000 portfolio with an average cost basis established around 2015, average annual CPI of 3%, and a full liquidation."

"Under current law, the entire nominal gain is taxed at long-term capital gains rates: 15% for most retirees, 20% plus the 3.8% net investment income tax for higher-income sellers. Indexing replaces the original purchase price with a basis grown by cumulative inflation, shrinking the taxable gain. What the math looks like A position bought in 2015 has roughly an 11-year inflation tail by 2026."

"At 3% compounded, a sizeable share of the nominal gain is purchasing power that never compounded in real terms. On the $500,000 liquidation, the difference between the unindexed and indexed tax bill runs into the tens of thousands of dollars, depending on the original basis and the seller's bracket. The savings scale directly with holding period and gain size. Inflation is still doing the damage in real time."

"Indexing benefits one group disproportionately: investors with large unrealized gains and long holding periods. Retirees holding appreciated index funds, founders selling a 25-year-old business, landlords exiting rentals bought in the early 2000s. Younger investors with shorter horizons see modest relief. Durability matters too. A Treasury regulation can be reversed by a future Treasury. Basis adjustments already claime"

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