Sage Intacct sync error: Transaction 'XXXX' can't be reclassified

Why the sync error occurs

This is due to an update to a paid invoice which cannot sync due to one of the reasons listed here, per Sage Intacct.

How to fix the sync error

Reason Solution
Application configuration and user permissions Company Configuration - Make sure the option to Enable reclassification of bills and adjustments is selected in AR or AP configuration:

Accounts Payable > Open Setup > Configure Accounts Payable
Accounts Receivable > Open Setup > Configure Accounts Receivable

User setup - Check your user setup.

Locate your user record and edit subscriptions.
In AP or AR, select the Permissions link and check that you can see the Reclassify link at the end of the transaction type, such as Bills and adjustments, or Invoices and adjustments respectively.
If you don't have admin or business user permissions to access or change any of the above options, contact your administrator.
Transaction types that can be reclassified You can reclassify the following transactions:

AP-bills and adjustments
AP-manual checks
AR-invoices and adjustments
AR-manual deposits

In addition, you can reclassify order entry and purchasing transactions if they affect AP and AR (sub-ledger) as long as you do it from the sub-ledger AP or AR side, and not from within Order Entry or Purchasing:
Reclassifying a bill or invoice that was generated in Purchasing or Order Entry does not affect the original PO or OE transaction. For example, in Purchasing you create a vendor invoice with a location of California, and in Accounts Payable you reclassify the bill and change the location to New York. Only the location listed on the AP bill changes to New York. The location listed on the originating vendor invoice in PO does not change; it continues to be listed as California. The listing of California is permanent. You cannot re-open the original vendor invoice and change the location manually.
Summary or period is closed Reopen the period or specific summary.
Transaction was processed and acted upon Best practice is to make a journal entry.
For example, an expense report was submitted for travel, then invoiced. In reality, it should have been submitted for meals. But because it was invoiced, it can't be reclassified. You can make a journal entry to correct the record.
Transaction is multi-currency Make a journal entry.
Transaction is reversed or in reversal state If you reclassify either transaction, the data becomes out of sync. The system can't update the transaction.
Transaction is unpaid You can edit unpaid transactions that are in an open period.
IGC company transaction created at the root Make a journal entry.
Transaction is paid by credit card Make a journal entry.
Line items with associated allocation Make a journal entry.
Manual deposits, manual checks, or quick checks where the accounting method is accrual and cash (multi-book) Make a journal entry.
Bank restrictions enabled Make a journal entry.
Inline credit for multi-entity company Make a journal entry.
Transaction is linked to revenue recognition or revenue allocation (AR only) It is possible to make a journal entry for all the individual recognitions and allocations, but there will be no link back to the original transaction, so you need to document well what you did and why.
Transaction payment associated with a deposit in an undeposited funds account (AR only) - Reclassify the entry prior to making the deposit.
- If you already made the deposit, make a journal entry.
Transaction is used in a company that is enabled for Sage Intacct simplified or advanced tax (AR only) Make a journal entry.
Transaction is used in a company that is enabled for Avalara (AR, OE, and Purchasing) Make a journal entry.