QB Issue Resolution:
What column in the Download Transactions window does the check number show up in? If it is in the name instead of the check number that is probably the issue – the bank is putting it in the wrong field.
Resolution for Issue 'When the transaction is added from on-line banking to the check register, check number gets deleted' available: Yes (Solved).
Source: Intuit Community forum.
When the transaction is added from on-line banking to the check register, check number gets deleted: 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 Banking
Quickbooks Repair Pro will resolve it efficiently and affordably. Guaranteed resolution of your issue, or you pay nothing!
Error Recovery for Banking [Canada]
E-Tech is the #1 Quickbooks data migration and Conversion service provider.
Additional Support Options: