I am doing my mom’s taxes...I know I procrastinated because every other year it was easy...but this year she had to sells some long-held stock to pay for her full-time dementia care. I have no id

[Critter-3]

You don't need an ID to enter stock sales off a form 1099-B from the broker ... make sure you are entering them in the correct place.  SKIP the import option ... enter them yourself ...

[RWM-001]

I'm guessing your question got cut off.  Were you going to say you have no idea what the basis of the stock is?  If so, you will just have to re-create the basis as best you can.  If you make a good faith effort, then you at least won't be subject to penalties for negligence.  For example, can you estimate when the shares were purchased?  At least what year and how many shares?  Then look up the stock price at that time.  You also need to consider the ownership history of the stock.  Did she inherit from someone?  Her husband maybe?  If so, there most likely was an adjustment in basis at the date of death.  You really need a tax professional to sort this out for you.