There are limits to how much you can contribute to your 401(k). These limits can change annually, and people over 50 can contribute more. Here’s what the 2020 limits are: The laws, rules and regulations depend on what kind of 401(k) you have. There are traditional, safe harbor and SIMPLE 401(k) plans. Each has different rules that must be followed. According to the IRS, “To qualify for the tax benefits available to qualified plans, a plan must both contain language that meets certain requirements (qualification rules) of the tax law and be operated in accordance with the plan’s provisions.”