I accidentally marked my GST dates wrong and "marked as filed", I need to change it so it matches what I filed with the CRA (correct dates) Everything was $0 either way

Hello @wornbythewater.

Since your sales tax return is marked as Filed in QuickBooks, you'll need to contact your accountant or bookkeeper to unfile it and help manage the taxes. 

Before unfiling, please note the following: 

• Only accountants and bookkeepers can unfile a sales tax return. 
• Only returns marked as Filed in QuickBooks can be unfiled. 
• Returns must be unfiled in chronological order, from newest to the oldest.
• Returns that were already successfully submitted to the tax agency cannot be unfiled.
• If you need to make corrections (for example, adjust the accounting period or fix an error), those corrections should be reflected on the next submission rather than by modifying a previously filed return.

If you don't have an accountant, you can contact QuickBooks Live Support Team, they can also assist with unfiling. 

Let us know if you have any other questions. We're here to help.