Forgot how I wrote my check last year to the pa department of revenue. What do I put in the memo section of the check?

For my income tax the instructions are telling me to put my SSN number on the check but there are no instructions like that on the pa department of revenue voucher that I had print out. What do you all put in the memo part of the check? Really don't want to put my SSN on the check. Feels like my identity is going to get stolen like that plus my SSN number is on the voucher itself so idk if I have to put on the memo of the check when it's already on the voucher.