It would be great to have an automatic warning if a duplicate product was entered on an invoice.

QuickBooks Online currently offers warnings if duplicate check or bill numbers are used.  It does not have a warning for duplicate invoice items.

Please submit your request for a duplicate product warning through the […]

Resolution for 'avoid duplications issue: 'is there a way to avoid duplications when entering products on an invoice' available: Yes.

The avoid duplications 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 avoid duplications issue yourself by looking for a resolution described in the article. If it is a complex avoid duplications issue or you are unable to solve the issue, you may contact us by clicking here or by using other avoid duplications support options.

For more information about resolving issues related to avoid duplications in Quickbooks/QBO or to get support for the issue 'is there a way to avoid duplications when entering products on an invoice', click the link below: