To add or change a tax type associated to a Custom Package:
Go to Center level > Admin > Organization > Centers > Center Name > Tax Groups > Select checkboxes for tax groups, as required > Save.
You can now view the newly associated tax types in the drop-down list for Custom Packages under Center level > Admin > Organization > Centers > Center Name > Invoice and Receipts > Tax Types for Custom Packages.
To create Tax Groups (so that they appear on the Center level under Admin > Organization > Centers > Center Name > Tax Groups):
Go to Organization level > Setup > Tax Groups> Add (As part of creating the Tax Group, ensure that you select the Active checkbox in the General tab and associate the required Centers in the Centers tab).