I would think so unless you own 5% or more of your employer's stock, since you are still working for the same employer. The law is very specific, you can delay your 401(l) RMD from your CURRENT employer is you are still working and don't own more than 5% of the company. Having said that, I believe your employer's 401(k) plan must include a "still-working" exception clause. So check with your employer.
Retirement plan and IRA required minimum distributions FAQs | Internal Revenue Service
Q1. What are required minimum distributions? (updated Dec. 10, 2024)
Required Minimum Distributions (RMDs) are minimum amounts that IRA and retirement plan account owners generally must withdraw annually starting with the year they reach age 73. Retirement plan account owners can delay taking their RMDs until the year in which they retire, unless they're a 5% owner of the business sponsoring the plan.
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Can you roll the old 401(k) from your employer plan into your union's 401(k)? If you can, that may alleviate your concerns.