Filing a decedents estate 1041 when one of the beneficiaries refuses to give their social security number.

Good Morning Community,

I have a question about filing a decedents estate tax return 1041.  The beneficiaries are two ladies who are half sisters and had the same father.  The estate is for their deceased father.  The lady that I represent I have her social security number.  The lady that I don't know refuses to give her social security number.  Can I paper file the return without her number and attach a letter stating that one of the beneficiaries refuses to disclose their s.s. number.  Would it be better is my clients attorney contacted the relatives attorney and ask for their s.s. number and if they refuse attach that letter.  My client is hesitant to contact their attorney because of their high hourly rate of $400 p.h.  I read that if you can attach a letter and explain that you tried to get the number you will not be penalized.  I also read that you can file without a s.s. number or letter of explanation and the penalty would be $50.  There was no income in the estate but there was combined legal fees of $10,000 to my client and $25,000 to her half sister which were paid or reimbursed just before they closed out the estate checking account in January - 2025.  It would be a shame if they didn't at least get a tax deduction on the final return for the estate.  What would some of the experts out in the community do?

Thanks for reading my question,

John Skouberdis