https://en.wikipedia.org/wiki/401(k)#History https://en.wikipedia.org/wiki/401(k)#History : "Congress [... enacted the ...] Internal Revenue Code Section 401(k)

https://en.wikipedia.org/wiki/401(k)#History https://en.wikipedia.org/wiki/401(k)#History : "Congress [... enacted the ...] Internal Revenue Code Section 401(k) as part of the Revenue Act.[8] This occurred on November 6, 1978."