Your beneficiary ID number is generally the same as your Social Security Number or Individual Taxpayer Identification Number, which you've already entered on your your income tax return in the Personal Info section of TurboTax.
Per IRS Instructions for Schedule K-1 (Form 1041) for a Beneficiary Filing Form 1040 Beneficiary's identification number:
For your protection, Schedule K-1 may
show only the last four digits of your
identifying number (social security number
(SSN), etc.). However, the estate or trust
has reported your complete identifying
number to the IRS.
