In this transaction you should assign tax codes which will be used for non-taxable transactions. Almost every country has business and/or government transactions for which not input or output tax should apply.
Transaction: OBCL
IMG Path: Financial Accounting (New) -> Financial Accounting Global Settings (New) -> Tax on Sales/Purchases -> Posting -> Assign Tax Codes for Non-Taxable transactions
Table: T001
When you open the transaction, find your company code and assign tax codes for input and output taxes as well as enter an jurisdiction code if such is necessary.