QB Issue Resolution:

create an item called opening balance and select an equity account or opening balance equity on the item screen

use that item on a credit memo for the customer, back date the CM

Resolution for Issue 'How do I correct a customer opening balance after I have recorded subsequent invoices without changing my bank balance?' available: Yes (Solved).
Source: Intuit Community forum.

How do I correct a customer opening balance after I have recorded subsequent invoices without changing my bank balance?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for bank balance
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Error Recovery for bank balance [Canada]
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