Problem:
if you are posting journal in GL. then you can get this warning.
Account number for Transaction type sales tax does not exist.
Reported from company account 'xxxx'
Solution :
You can check in below areas: -
1) If main accounts are selected in the "Ledger posting group" form in Tax module!
2) check in inventory posting profile setup and select the main account for sales tax posting type. this is for PO or SO?
3) Check in main account which posting type you have selected. this should be "Sales tax".
point 3 will be cleared if you already set point 1 as without selecting posting type as "Sales tax" in main account level, system will not allow you to select any account in "Ledger posting group" form.