To apply tax to a revenue item, a tax item must first be created.
Go to Admin > Manage Codes > Revenue Codes > Revenue Items.
Create a new revenue item. This revenue item will act as a tax item that can be added to other items when applying tax. Set Is This A Taxable Item? to Tax, and enter the tax percentage.
Then, find the revenue item that the tax will be applied to, and mark it as a Taxable Item.
Select Action > Set Tax Items, select the new tax revenue item, and save.
When that taxable revenue item is used on an invoice (such as through a Pledge Campaign), the tax will be automatically applied as a separate revenue item.
