
Tax Code should be valid for A/P
You have tried to assign a tax code that is not applicable for purchasing documents to a row in the purchasing document that you are creating.
From the SAP Business One Main Menu, choose . The Tax Codes - Setup window appears.
Find the tax code you need to use in the purchasing document, and in the Valid for area, select the option Purchasing.
Choose Update, and then reassign the tax code to the relevant row in the purchasing document.