Hi Margaret14,
Thank you for reaching out.
If your accountant has been invited into your QBO file, he or she would have the accountant tool to re-classify transaction in bulk. To find QBO certified accountants or bookkeepers near you, please visit:
Alternatively, you can ran a transactions without GST report to identify which transactions are missing GST codes, but you'd still need to do it one by one.
Please let us know if you have any questions.