CP268 tells you we made changes to your return because we believe there is a miscalculation on your return. You get an overpayment credit when your tax payments exceed what you owe.You'll automatically receive a refund of the credit. You can find the CP or LTR number on the right corner of the letter. You received this notice because the deposits or payments applied to your account didn't agree with what you claimed on your federal tax return. This form is for general instructions that apply to all corporation tax forms. It includes a variety of topics about how to fill out your form. Step 1: Complete the taxpayer information section. What this notice is about. You have a remaining balance due on a tax period after an overpayment (offset-in) was applied to your account.