The amount of elective deferrals that an individual can exclude from income for a tax year is limited. Elective deferrals are: 
(1)  amounts contributed to tax sheltered annuity plans under salary reduction agreements;
 (2)  amounts contributed under cash or deferred arrangements to 401(k) plans ( Q 3751) and salary reduction SEPs (“SAR-SEPs”) ( Q 3705); and
 (3)  amounts contributed under salary reductions to SIMPLE IRAs ( Q 3706).1
 Elective deferrals do not include elective contributions made pursuant to a one-time irrevocable election that is made at initial eligibility to participate in the salary reduction agreement or pursuant to certain other one time irrevocable elections specified in regulations, or pre-tax contributions made as a condition of employment.
2  For 2020-2021, the aggregate limit on elective deferrals was $19,500, and the limit for 2022 is $20,500. The limit increased to $22,500 in 2023, $23,000 in 2024 and $23,500 in 2025.
3 The elective deferral limit is indexed for inflation in increments of $500.
4    
  1.  IRC § 402(g).  
2.  IRC § 402(g)(3).  
3.  IRC § 402(g)(1); Notice 2017-64, Notice 2018-83, Notice 2019-59, Notice 2020-79, Notice 2021-61, Notice 2022-55, Notice 2023-75, Notice 2024-80.  
4.  IRC § 402(g)(4).