I could not find an one location that would answer this question, but I did find some info spread around several locations.
On the SSA benefits planner site:
When you apply for benefits, we'll need the following:
- Your Social Security number;
- Your birth certificate (If you don't have a birth certificate, you can get one from the state where you were born. Go to What Documents
Will You Need When You Apply? for more information.);
- Your W-2 forms or self-employment tax return for last year;
If our records show that documents proving age or citizenship/lawful alien status have already been submitted for an
earlier Medicare or Social Security claim (such as Disability,
Supplemental Security Income, etc.), you do not need to submit the
If you are applying in early 2020 then they need to know about your 2019 earnings, that is why you bring the W-2.
Your employer submits to the SSA your actual values by the last day of January they using form W-3. The same page says that the employer can give the employee the W-2 earlier if they are done working for the year, it doesn't mention sending in the W-3 early.
That would mean the the Social Security Administration will not know about your 2020 income until after January 2021. There might be a delay between your employer submitting the forms and it appearing in your account history.
I imagine that your situation is rare because most people hit 40 credits in their 20's or 30's. You may be able to find assistance with a service that handles elder care issues, they may understand how to handle situations like yours.