26 CFR § 1.1240-1 - Capital gains treatment of certain termination payments.
Any amounts received by an employee for the assignment or release of all his rights to receive, after termination of his employment and for a period of not less than five years or for a period ending with his death, a percentage of the profits or receipts of his employer attributable to a time subsequent to such termination, are considered received from the sale or exchange of a capital asset held for more than six months if the following requirements are met:
(a) The employee was employed by the employer, in whose future profits or receipts the employee had an interest, for a period of more than 20 years before the assignment or release by the employee of his rights in such future profits or receipts,
(b) The full rights of the employee to the percentage of the future profits or receipts on such employer, which rights are the subject of the assignment or release, were incorporated in the terms of the contract of employment between the employee and the employer for a period of at least 12 years, and were so incorporated before August 16, 1954,
(e) The total amount to which the employee became entitled pursuant to the assignment or release was received by the employee after the termination of his employment with such employer and in one taxable year of the employee.