You're also subject to the annual employee contribution limit, which is $19,500 in 2021, or $26,000 including catch-up contributions if you're 50 or older. In other words, you can contribute up to those limits, but never more than your earned income. If you make $15,000 in self-employment income this year, that's the most you can contribute as an employee. Note, too, that these employee contribution limits apply to your cumulative deposits made to all 401(k) accounts. If you also have a regular job and put $10,000 in a workplace 401(k), for example, the most you can contribute to your solo 40...