Estimate change orders are not stored in a table.You cannot link the cost of a particular item in a PO or bill to a particular item on a customer invoice. Cost of a specific inventory item is not available.It doesn't record WHERE it has been billed. QuickBooks only changes the status on the bill to 'has been billed'. There is no link between a particular bill item/expense that has been billed to a particular customer invoice. Customer Invoices are not linked to Vendor Bills.Much of it has to do with the logistics of adding volume to a small business application like QuickBooks, other times, it requires complexities that are only found in higher end accounting programs. As you will see below, this is not always the case. Users often make assumptions that because they 'see' things when they use QuickBooks, that the database operates in a similar logical manner. Intuit does not give developers direct access to the QuickBooks database, but have exposed 98% of the available fields through its SDK QuickBooks Analytics Limitations It is not an Intuit sanctioned method for extracting data in a 3rd party application and does not include all of the available data. In 2011, Intuit added an additional Custom Reporting feature for Enterprise users that allowed a more direct access to QuickBooks.
In 2001, Intuit first opened up access to their product data with the introduction of their Software Development Kit (SDK), but it is not a direct connection to the database rather it is an XML extraction which can be slow on large files.
QuickBooks Desktop Data Availability and Design