User preferences for your invoicing reference can be configured to be prefilled in all your invoices. You can set whether you would like your invoice to display either the Quote Number or the Project Name.
The Invoice Reference Prefill field config variable can be located under Admin /Extra/Config. You can make use of the search tool bar- located bottom right of the screen and search for ‘INVOICE REFERENCE’
Once the search is run, you will see that the INVOICE_REFERENCE_PREFILL_FIELD config variable appears. You can then double click on this variable to make adjustments to suit you preferences.
The options available for this config are QuoteNumber (1) or ProjectName(2) . These options can be typed into the ‘value’ section of the edit config variable as shown below.