The ACH, electronic routing number is 9 digit, all number code that identifies each US bank. This is the number we need when you pay in to TransferWise ACH Bank Debit.
Most US bank have two, separate routing numbers - a wire routing number and an a ACH routing number. If your routing number isn't being accepted when setting up a transfer on your profile, it's worth checking to make sure you are entering the correct one - the ACH routing number.
This page gives some guidance on how to find the ACH routing number.
Very occasionally, banks use the same number for wire and ACH transfers. So, when asking, please be sure to specify that you need to make a transfer via ACH.