Batch change out of scope of GST to inclusive of GST

I forgot to active GST for my client before I accepted all the transactions into accounts. Now I realized that and active GST and when I try to reclassify transactions with correct GST code, the system says because the default tax rate is out of scope of gst, I cannot batch change transactions tax code. I clicked into the transactions one by one to change the gst rate from out of scope of gst to inclusive of gst. And after that I can reclassify transactions' gst code as purchase 10% or sales 10%. Just want to know is there any way to change accepted transactions' gst rate from out of scope to inclusive of gst in one time? I still have many transactions that need to be corrected. I have already changed the default tax rate selection in advance setting. However it doesn't work on the transactions that already accepted. Thank you.