• Quickbooks Error Code (6240): The name supplied already exists. Another customer, supplier, or employee is already using this name. Please use a different name.


  • Syngency

  • Quickbooks Online

Additional Information:

  • Please note that when merging the Contacts you must ensure that the Contact with the Syngency ID is the one that remains active. The original Contact in Quickbooks is the one that will need to be merged into the one with the Syngency ID.

  • For a full list of Quickbook Error Codes click here.


This indicates that another Contact already exists in QBO with an identical Display Name. You will need to merge these Contacts within Quickbooks.


  1. Change the name of the Contact in Quickbooks. Example: John Doe to John1 Doe

  2. Visit the Quickbooks error code and click the Re-Sync button -or- wait a full day for Syngency to try to sync over John Doe again

  3. Within Quickbooks navigate to John Doe

  4. Select Edit

  5. Copy John Doe within the Display name as field

  6. Navigate to the original John1 Doe in Quickbooks Online

  7. Select the Edit button

  8. Paste John Doe into the Display name as field

  9. Select to save the Contact

  10. Select Yes within the prompt that asks if you would like to merge Contacts

If the above steps do not work, you can also attempt to change the Invoice ID Number. This process can be done either in Syngency or in QBO. It may be best to look into making this change in QBO as the invoices in QBO are not Customer Facing. To make this change in Syngency, please follow the steps below:

  1. Navigate to the Bill you would like to Edit

  2. Click More Actions at the top right and select Edit

  3. At the top left click on the ID# field and enter desired Invoice Number

  4. Click Update Invoice

To change an invoice number in QBO follow the steps below:

  1. Go to Sales or Invoicing, then click on the Invoices tab.

  2. Select the invoice in question.

  3. Go to the Invoice no. field and change the invoice number.

  4. Click Save and Close or Save and Send.

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