The IRS caps the maximum annual contribution that you can make to any 401(k) plan at $19,500 for 2020. You can contribute to an IRA in addition to your 401(k). How long you can contribute depends on how old you are when you start making contributions. You can begin contributing to your traditional 401(k) account when you start working, typically at age 18 or older, but the maximum contribution limit for any year is $19,500 if you are under 50 years old in 2020.