A CP80 notice means that the IRS has credited payments and/or other credits to your tax account for the tax period shown on your notice, but they haven't gotten your return for that period.
You can claim the payments/credits if you file the prior year return indicated on the notice. Keep in mind that there's a time limit to filing prior year returns and, depending on the situation, there could be money owed, fees, and penalties. Send your signed return to the address shown on the top of your notice.
For additional questions regarding your notice, contact the IRS.