Two options are available that mean your client will not be charged for time. However, they have distinct differences when it comes to billing.
No charge – When an invoice is generated from Unbilled Activity, time entries will be included on the invoice with a 100% discount.
No charge don't show – The entry shows in the Time section, but will not be available to be added to a new invoice. It also will not affect areas such as Uninvoiced Time totals or the dollar amount totals in the Work In Progress report.
Note: Matters listed with a billing option of Flat Fee Based Only, Contingency Only, or Not Billable automatically have No Charge Don't Show selected when creating new Time Entries.