Tax Alpha Insider

Tax Alpha Insider

Margin call me maybe

New products using margin deliver tax efficiency, but at what cost?

Brent Sullivan's avatar
Brent Sullivan
Sep 28, 2025
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Carly Rae advocating for prudent risk management

Two of the hottest trends in private wealth are tax-aware long/short and borrowing via box spread.

Both have substantial pre- and post-tax perks, and both use margin.

That’s fine… when prudently managed.

This week, I’m taking the tax benefits of these products for granted and instead asking…

Is margin call risk a big deal?

Mentioned in this article…

  • NBER (Gary B. Gorton & Andrew Metrick): Securitized Banking and the Run on Repo

  • Basel Committee on Banking Supervision: Review of margining practices

  • Firstrade: Margin Loans (several worked examples)

  • AQR: Experience Matters: Addressing Five Common Criticisms of Tax Aware Long-Short (TA LS) Strategies

Underwriting margin call risk

  1. What could go wrong?

  2. Not all margin call risk is the same

  3. Why should we care about margin calls?

  4. What could cause a margin call? (6 rug-pulls)

  5. Who’s in charge of the margin?

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