What these notices are about We sent you a CP180 or CP181 notice because your tax return is missing a schedule or form. What you need to do Read the notice carefully to determine the required schedule or form needed to complete your return. Download the required schedule or form or call 800-829-3676. Fill out the Contact Information section of the notice, detach, and send it to us with your completed schedule or form so we receive it by the date indicated on the notice. You may want to Review the filing requirements and instructions for the missing schedule or form to determine whether your organization needs to file. Review your records to ensure all applicable schedules and forms were attached when filed. Frequently Asked Questions What happens if I don't respond by the due date? If you don't respond by the due date of the notice, your tax and/or credits may be adjusted which may result in a balance due. Who do I call for assistance? For assistance with your business return, call 800-829-0115 or, for assistance with Form 990-T, call 877-829-5500. Helpful information Publication 542, CorporationsPDF Publication 559, Survivors, Executors, and AdministratorsPDF Publication 598, Tax on Unrelated Business Income of Exempt OrganizationsPDF Tips for next year Refer to the instructions for your tax return for required documentation. Attach all required forms and schedules to your tax return when filing. Consider filing your taxes electronically. Filing online can help you avoid mistakes and find credits and deductions that you may qualify for. In many cases you can file for free. Learn more about e-file. Reference tools Publication 1, Your Rights as a Taxpayer Full list of tax forms and instructions Need help? You can authorize someone to contact the IRS on your behalf. See if you qualify for help from a Low Income Taxpayer Clinic. If you can’t find what you need online, call the IRS number at the top of your notice or letter.