That would be an error in oyur W-2.
There is indeed a code of C for taxable group term life insurance over $50,000 and a code of P for nontaxable moving expenses. There is, however, no code CP. Since box 12 codes do usually have some impact on your return,it is important that they be correct. You will, unfortunately have to ask your employer what this is supposed to be and probably get a corrected W-2 from them.
