ProntoForms now offers direct integration with QuickBooks. Click here to learn how to use this feature.
If you are using QuickBooks with ProntoForms you can interchange data between both systems using the CSV exports of both systems. Exports from QuickBooks can be become data sources for a ProntoForms form. (Learn more about data sources.) And CSV exports from ProntoForms can be imported in QuickBooks using this handy manual from Intuit. You will need to map the fields from your ProntoForms form to fields in QuickBooks to achieve this.