You can set the default Tax and Surcharges for generating invoices using the the "TimeTracker Flags".

To set the default Tax or Surcharges

  • Click the TimeTracker Flags tab in Salesforce
  • Search for "invoice-header-tax-rate", enter the Tax rate in Number Value, and Save it.
  • You can add the surcharge rate using the "invoice-header-surcharge-rate" flag.

The rate that is added in the Invoice header tax rate and invoice header surcharge rate is automatically added to the invoices that gets generated in your org.