Reason why NetSuite prints “Customer to pay Output Tax” message on the transactions.

The reason as to why NetSuite prints "Customer to pay Output Tax" message on the transactions is that the transactions includes Reverse Charge Tax Code (UK & EU Countries).

1. Navigate to Setup > Accounting> Tax Codes> View the Tax Code for UK & EU Countries.
2. If Reverse Charge Code box is checked this will print the "Customer to pay Output Tax" message on the transactions.