Do you mean because the software won't let you adjust sales tax amount when using the module to post tax amounts on bills, invoices, expenses, etc? Would you, in theory, be able to use JEs if you avoided the tax module altogether (i.e., set up corresponding asset and liability accounts; GST collected - ITCs as a Dr to that asset account when posting an expense along with corresponding Cr Cash and Cr GST Payable liability)? Or are you basically re-creating what QBO has already created for you in providing the tax module? 

Sorry if this is confusing or deserves to be in another thread all its own!

Thanks,