In order to allow for the proper calculation of tax in both Manage and Sage 50 Accounts, you need to map the Tax Code you have set up in Manage to the tax code you have set up in Sage 50 Accounts. Manage allows for multiple levels to be defined for each Tax Code, but you will only use the first level of the Tax Code. Sage validates that only 1 tax level has a tax code. Multi-level tax is not supported by Sage.
The “Tax Code Xref” field of the System > Setup Tables > Tax Codes screen in Manage should be consistent with the “Code” (T0, T1, etc.) in the Settings >Configuration > Tax Codes in Sage 50 Accounts.
When dealing with “Tax Exempt” tax rates, you will still need to fill the first Tax Code XRef field to match the Tax Group in Sage 50 Accounts. The following is an example of a Tax Exempt setup: