Look like there is a bug in HR Expense. It doesn't account for more than one child tax base account. I tested it on Odoo V9 demo and it has this problem too. I have two taxes in my province, GST and PST. Both taxes are child taxes under the parent purchase tax code. After I click the "Generate Accounting Entries" button in the HR Expense module, it registes PST Paid, GST Paid, and Base of PST accounts, but not Base of GST.

I want to see if other people are having this same issue before I report it on GitHub.