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New IRS Procedures for Retirement Plans: Cycle 4 Opinion Letters & Adoption Deadlines
Employers managing defined contribution or defined benefit plans face new IRS deadlines and requirements under the remedial amendment Cycle 4—in this article, clarity on what’s changing and when to act.
By NomadicTax Research Team • 5-8 min read • August 27, 2026
## What is Cycle 4 under Rev. Proc. 2023-37?
The IRS uses remedial amendment cycles to update pre-approved plans so that they conform to the latest law changes. **Cycle 4** applies to defined contribution qualified pre-approved plans (and defined benefit plans under separate guidance), incorporating recent qualification requirement changes. This ensures adopted retirement plans comply with all relevant Internal Revenue Code (IRC) and regulatory standards. ([irs.gov](https://www.irs.gov/pub/irs-irbs/irb26-35.pdf?utm_source=openai))
## Key Changes & Deadlines
- The IRS will issue **opinion letters** for Cycle 4 defined contribution plans, updated in line with the 2023 Cumulative List, filed during the Cycle 4 submission period. Dates expected around **August 31, 2026**. ([irs.gov](https://www.irs.gov/pub/irs-irbs/irb26-35.pdf?utm_source=openai))
- Employers must **adopt implemented plans** by **September 30, 2028**, or they lose eligibility in Cycle 4. ([irs.gov](https://www.irs.gov/pub/irs-irbs/irb26-35.pdf?utm_source=openai))
- Application window for **individual determination letters** opens October 1, 2026, and ends September 30, 2028, for certain adopting employers. ([irs.gov](https://www.irs.gov/pub/irs-irbs/irb26-35.pdf?utm_source=openai))
## What Employers Need to Do Now
1. **Review plan qualification changes** listed in the 2026 Cumulative List (both defined contribution and defined benefit plans) to see what updates your plan requires. ([irs.gov](https://www.irs.gov/pub/irs-drop/n-26-34.pdf?utm_source=openai))
2. Work with plan counsel to implement amendments before **September 30, 2028**.
3. If eligible, prepare to file for determination letters during the **October 1, 2026-September 30, 2028** window.
4. Monitor IRS announcements—opinion letters expected around **August 31, 2026**, for defined contribution plans. ([irs.gov](https://www.irs.gov/pub/irs-irbs/irb26-35.pdf?utm_source=openai))
## Practical Example
Acme Manufacturing has a defined contribution plan that hasn’t been updated since 2022. In early 2026, Acme reviews the 2026 Cumulative List and identifies changes related to discrimination testing and nondiscrimination relief. They engage a retirement plan attorney to amend the plan document and adopt the updated plan by **December 2027**, ensuring they remain eligible under Cycle 4 and can file a determination letter after October 2026.
## Compliance Risks If You Miss the Window
- Failure to adopt updates by **September 30, 2028** may result in disqualification of the plan’s tax-favored status.
- Missed opportunity to get IRS opinion letters, which are valuable for demonstrating plan compliance.
- Potential for costly restatement or exposure to penalties or tax liabilities for employees.
## Tips for Success
- Start early: amendment drafting takes time, especially for large or complex plans.
- Ensure thorough communication with all service providers (record-keepers, actuaries).
- Use the 2026 Cumulative Lists as your checklist.
- Engage professionals who specialize in employee benefits law to avoid pitfalls.
By staying ahead of the deadlines and fulfilling all adoption and filing requirements, employers can ensure their retirement plans remain valid, beneficial, and compliant under Cycle 4.