Hi Jing:

To elaborate a little on Support's answer, the AR Year-End process can only proceed once all accumulated GL transactions currently sitting in AR are cleared.

How the transactions are cleared depends on whether you have a set of GL books linked to AR.

Most users have GL linked to their AR. If you do, then go to the GL module and Retrieve the transactions from AR. This clears them from AR and your Year-End can proceed.

However if you do not have a GL linked, the expectation is that you would print a report of GL transactions, then clear the report. After you print the report, you will be asked if you want to clear the report. Once you do that, your AR Year-End can proceed.