A\R Balance on Cash Bais Trial Balance

I would filter the AR Report to locate any transactions that are out of the ordinary and then backtrack from there. Possibly a Journal entry or deposit / checks that were posted there.

There may be nothing to trace; this is not necessarily an error.

If the charges on unpaid invoices hit another balance sheet account, this shows on Cash Basis.

For instance, if this client sells Inventory items; collects against Liability accounts or loan (asset) account; if ths client charges for reserves, such as an HOA; does Trust accounting or Retainage for construction; if this client uses the invoice method to charge customers for an NSF fund per the Help instructions...

All of that means, the AR side is one balance sheet account and the "other" side is balance sheet, too. Both must show, on Cash basis, for the balance sheet to be correct.

Adjusting it affects your client's data. Are they getting back their file? You will have impacted their ability to manage that this customer owes. You can change the date to the new year, or offset it with a Credit Memo. Don't use journal entries for AR, AP, inventory.

Adjusting for it can be done for tax form filing purposes without affecting the QB data.

For instance, if you sold Inventory on an invoice that is unpaid, the inventory asset account and COGS need to be correct, which means the AR is going to show. If you charge for Retention (other asset for builders) then the Other Asset balance is not correct unless the AR shows. You can't have one without the other.

Here is the most obvious example: An invoice that charges the bank account for NSF check, per the Help instructions. Two asset accounts.

Double-click the total AR on a cash basis balance sheet, then filter it to Open status only. Look at what accounts are hit by the items on these transactions.

Tax preparation might need to take some of this into consideration. That is why it is called "modified accrual basis" for some tax filers.