The client invoice will display the invoice due date dependent on your payment settings. You are able to adjust/change the default due time period on an invoice.
1. Go into your 'toolbox' and click on 'Admin'.
2. Select 'Company Info
3. In the Payment Terms text box, change the numbers that are displayed. For example if your current setting is 'Net 30' and you want to change it to 'Net 60', change the number to 60 and by default the invoice will do 60 days out from the invoice date. Don't forget to select 'Update' to save changes.