A CP23 notice means the estimated tax that you reported on your tax return is different from what the IRS has a record of receiving. If you paid the amount listed as due on the CP23 form you would not have to prepare an amended return unless you thought the CP23 notice was in error.
When you completed the amended return if you included the tax you paid with the CP23 notice and it indicated that you were due a refund, then you should receive that refund amount.
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