What is the joint filing income maximum to allow eligibility to participate in a 401K?

[magubj]

What is the limit of AGI which excludes participation in a 401K?

[DoninGA]

There is no AGI limit for a 401(k).  

Go to this IRS website for information - https://www.irs.gov/retirement-plans/401k-plans-deferrals-and-matching-when-compensation-exceeds-the...

Compensation and contribution limits are subject to annual cost-of-living adjustments. The annual limits are:

• salary deferrals - $19,500 in 2020 ($19,000 in 2019), plus $6,500 in 2020 ($6,000 in 2015 - 2019) if the employee is age 50 or older (IRC Sections 402(g) and 414(v))
• annual compensation - $285,000 in 2020, $280,000 in 2019 (IRC Section 401(a)(17))
• total employee and employer contributions (including forfeitures) - the lesser of 100% of an employee’s compensation or $57,000 for 2020 ($56,000 for 2019 not including "catch-up" elective deferrals of $6,500 in 2020 ($6,000 in 2015 - 2019) for employees age 50 or older) (IRC section 415(c))