This article applies to QuickBooks Online only. If you use the Deposit or Prepay feature in SingleOps and your credit memos are not syncing, or you see a duplicate document number error (error 6140), the Custom Transaction Numbers setting in QuickBooks Online is the most common cause.
🛑 If you use the Deposit or Prepay feature in SingleOps, Custom Transaction Numbers must be turned OFF in QuickBooks Online.
Why won't my deposit or prepay credit memos sync to QuickBooks?
When a deposit or prepayment is paid, SingleOps syncs a Sales Receipt to QuickBooks Online. When the deposit or prepayment is applied to an invoice, SingleOps syncs:
The invoice
A Credit Memo that deducts the amount from the Sales Receipt
A $0 payment that links the Credit Memo to the invoice
The Sales Receipt and Credit Memo share the same number (i.e. Sales Receipt SO-505 is tied to Credit Memo SO-505). If Custom Transaction Numbers is turned on, the Sales Receipt will sync but the Credit Memo will not. The Credit Memo fails with error 6140, a duplicate document number error:
Duplicate Document Number Error: You must specify a different number. This number has already been used.
To fix a credit memo not syncing or a duplicate document number error, turn off Custom Transaction Numbers using the steps below.
How do I turn off Custom Transaction Numbers in QuickBooks Online?
Log in to your QuickBooks Online account.
Click the Settings gear icon in the top right corner.
Click Account and Settings under Your Company.
Click Sales
Click the Edit icon next to Sales Form Content
Toggle Custom Transaction Numbers to OFF
Click Save, then click Done
What should I do after turning off Custom Transaction Numbers?
Resync your errors. In SingleOps, go to Reports > QB Syncing > QuickBooks Online Sync Report and resync any error 6140 or duplicate document number errors.
Check your Deposit Item. Your Deposit Item must be linked to an Other Current Liabilities account in QuickBooks Online, such as Customer Deposits. It must also be selected in SingleOps under Setup > Account Settings > QuickBooks > General Ledger Settings > Deposit Item. If the Deposit Item is missing or set up incorrectly, credit memos cannot link to invoices. For full setup steps, see Deposits.
⚠️ Do not manually create credit memos in QuickBooks Online using SingleOps numbers (such as SO-505). This causes duplicate document number errors when SingleOps tries to sync its own records.
💡 Some deposit or prepay corrections require temporarily turning Custom Transaction Numbers back on. If you are adjusting a deposit or prepay record and run into issues, contact SingleOps Support.
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