Hi Guys, What is the best way to add Tax. on the Vendor Bill ? I want to add as a line Item. What item type should i select to create one ?\

Is this US domestic tax only? You should install the proper tax bundle first. Once the tax bundle is setup and the nexus is established, you'll be able to connect proper tax codes to transactions that connect the native tax reporting functionality in NetSuite. International tax will have country-specific requirements.