Yes.
If you have additional evidence to support your position that has not been considered in the Stage 1 determination you can send the additional information to MyCSP. MyCSP will review the additional information that you submit and confirm if the original decision is changed in any way.
If you do not agree with the first stage decision you can appeal to Cabinet Office acting for the Scheme Manager, for a second stage decision. You can find out how to apply for a Stage 2 decision in the above questions.