Warner Bros. Discovery CEO David Zaslav‘s potential payout of more than $800 million from the Paramount Skydance deal highlights an obscure tax rule originally designed to limit CEO pay.

According to SEC filings, Zaslav could collect hundreds of millions of dollars in severance and other stock awards and payments following Paramount’s acquisition of WBD. The payments include about $500 million in share awards, about $115 million in vested stock awards and $34 million in cash, according to the filings.

The deal also includes up to $335 million in potential payments to Zaslav for what’s known as the “golden parachute” excise tax. The tax was originally created by Congress in the 1980s to limit what many considered to be outsized payouts to chief executives upon a change of control or sale of their companies. The tax, of 20%, kicks in when an executive’s payout exceeds three times their typical base salary and target annual bonus.

As part of the acquisition, Paramount agreed to pay Zaslav’s excise tax if his other payments trigger the tax. The reimbursement declines over time and drops to zero if the deal closes in 2027. Paramount has said it is aiming to close the deal, pending regulatory approval, by this fall.

The Paramount board said the reimbursement would be paid by Paramount, not Warner shareholders.

Without the payment, known as a “gross up,” the board said “Mr. Zaslav would be at a substantial disadvantage in terms of excise tax exposure relative to the previously proposed transaction with Netflix,” which wouldn’t have involved a golden parachute tax.

Zaslav’s payout from the deal is expected to be around $667 million without the tax.

Management experts have said that rather than limiting pay, the golden parachute rules have instead incentivized CEOs to sell their companies and reap ever-higher rewards. The tax has also led companies, and their shareholders, to spend even more to pay the special taxes.

“Over time, especially as executive compensation radically shifted toward stock-based pay, golden parachutes have become increasingly lucrative, platinum in many cases,” Jeffrey Gordon, co-director of Columbia Law School’s Ira M. Millstein Center for Global Markets and Corporate Ownership, wrote in a paper. “Even if there is pain among those who are laid off when the firm is sold and layoffs occur, there is plainly one winner: the CEO with a golden parachute.”

Correction: Paramount Skydance is acquiring Warner Bros. Discovery. A previous version of this story mischaracterized the deal.