Cash-in code pearson edexcel

Cash-in codes when to apply

I will be giving my ial exam of chemistry, biology, and physics, so i need to ask about the cash in codes. I'll be appearing in October session. Im giving all 3 units for chemistry Unit 1,2,3 for Chemistry. Biology and physics im giving unit 1 and 2. For unit 3, i will be giving in January 2027 series. So which cash in code should i use for chemistry and should i apply the cash in code for physics and biology in this oct session, or should i use the cash in code in January, when i will complete the entire course of AS level. And whats the cash in code for all of the 3 subjects? im a private candidate, switched from Cambridge to Pearson edexcel, so i got no idea.