How do import a Bill with both item entries and expense entries.  I see the tables and understand how to push the data in but not how the link is created betweeen entries in BillExpenseLine and BillItemLine tables so that in QB they are the same bill but on the different tabs.

Thanks

It's actually simple, but you need to first create either the Expense or Item lines first and then add the Item or Expense lines afterwards like this:

Step 1 - Create the Expense Lines
INSERT INTO "BillExpenseLine" ("ExpenseLineAccountRefListID", "ExpenseLineAmount", 
"ExpenseLineMemo", "FQSaveToCache")
VALUES ('120000-933270541', 436.07,
'Expense Line Memo Test', 1)

Step 2 - Write the Bill Header
INSERT INTO "Bill" ("VendorRefListID", "APAccountRefListID", "TxnDate", "RefNumber",
"TermsRefListID", "DueDate", "Memo")
VALUES ('10000-933272655', 'C0000-933270541', {d'2007-10-01'}, '905',
'10000-933272658', {d'2007-10-31'}, 'Test Expense and Item Lines')

Step 3 - Determine the TxnID of the new Bill
sp_lastinsertID Bill

Step 4 - Use the TxnID to append Item lines to the existing Bill
The LastInsertID returned was: 5CAD-1197762987

INSERT INTO "BillItemLine" ("TxnID", "ItemLineItemRefListID",
"ItemLineDesc", "ItemLineCost",  "ItemLineAmount")
VALUES ('5CAD-1197762987', '250000-933272656',
'Building permit 1', 1.00000, 1.00)

This results in the following Bill in QuickBooks with both a Expense and Item line:

The documentation states that the TxnId is not insertable.  I haven't tried it yet but am wondering to you mean the first field in the record TXNID ?