QuickBooks & osCommerce Integration

Yes. osCommerce is self-hosted and open source, so the integration works against the store database and admin API rather than against a hosted service. That covers the long-running 2.3 line and the community Phoenix builds, including stores carrying years of custom contributions.

It is the normal case. Most osCommerce stores still trading have accumulated custom modules and altered tables over the years. Because the mapping is defined per store rather than assumed, renamed fields and extra columns are handled at configuration time instead of breaking the sync.

An order becomes a sales receipt or an invoice depending on whether payment was captured at checkout, with each product as a line item, shipping and handling on their own lines, and tax posted to the mapped tax code. The customer record is created or matched first, so no transaction is left unassigned.

On a schedule you set: every few minutes for stores that need near-live figures, or once nightly for stores that only need the accounts to be right by morning. A lower frequency puts less load on a shared hosting account, which matters for older osCommerce installs.