Reject code R0000-504-02 means that the dependent's Social Security number or last name does not match the IRS records. So the SSN could be correct but the last name is wrong. Check the spelling carefully, especially the first four letters of the last name. It has to match the last name on his Social Security card, or on a recent Form SSA-1099 or letter from Social Security. If your father has more than just one first name and one last name, what the SSA thinks is his last name might not be the same as what you think is his last name. If either your daughter or your father changed their name, that could also lead to a mismatch.
