I am trying to change a single item to have a different tax rate then rest of invoice and I can't figure out how!!
The tax rate is set on the invoice itself so every Item on an invoice will use the same tax rate. However, you can make individual items non-taxable so they're not included in the overall tax rate. If you need to charge a different tax rate on a specific item it needs to be on a different invoice with that other tax rate.
Hope this helps and please let us know if you need any additional assistance.