Short Term Disability

I typed your words into Chatgpt and here was the response.
Yes — in many cases, your DH can receive his employer’s Short-Term Disability (STD) benefits while also applying for Social Security Disability Insurance (SSDI). The important thing is that the two programs have different rules, and the employer’s STD policy may have its own requirements.

SSA specifically says that private disability insurance benefits generally do not reduce SSDI. 

The important issue is the date he stops working

If his last day he can actually work is November 27, 2026, I would not wait until December to notify the employer/STD carrier.

Typically, the STD claim should be started when his disability causes him to stop working, or according to the deadline in his employer’s STD policy. The exact filing deadline is controlled by the policy/plan documents. The Department of Labor says the plan’s Summary Plan Description (SPD) should explain how and when disability claims are filed. 

So, practically, I would recommend:

Before November 27

• Contact his HR/benefits department.
• Tell them his Alzheimer’s has progressed to the point that he will be unable to continue working after November 27.
• Ask for the STD claim paperwork and the plan’s Summary Plan Description (SPD).
• Ask specifically: “What is the disability date, elimination/waiting period, and deadline for submitting the STD claim?”
• Have his treating physician complete whatever medical certification the STD carrier requires.

November 27

• This would generally be the date his disability begins if that is the first day he is unable to perform his job because of Alzheimer’s.

After that

• The STD claim can provide income while the SSDI application is being processed.
• SSDI has a 5-month waiting period before benefits can begin, although the exact timing of his entitlement depends on SSA’s established disability onset date. 

One very important distinction

You said he plans to “go on Social Security Disability starting in December.”

He can apply for SSDI before December. In fact, he doesn’t need to wait until he has been off work for months to apply. The key question for SSA is whether his condition prevents substantial work and is expected to last at least 12 months. 

And because he has early-onset Alzheimer’s, I would strongly recommend making sure the medical records clearly document why he can no longer safely and reliably perform his job, rather than simply documenting the diagnosis