Core charge is refundable when you return old battery (same battery you purchase from them when the batt is dead).You must be talking about auto parts stores? I buy my batteries at costco and have for many years. They just charge $15 core charge on any battery they sell. Last one bought in 2024 was still just $15 core charge. They don't need a receipt. They just look it up in their system.
It's basically same as beer bottles deposit you pay when you buy beer and get the deposit back when you return empties.