International Electrical Certification
This appears to be your client's problem. It is for them to specify the standards to which the product will be built and certified - you cannot be expected to anticipate what they will do with the product, unless that is part of the design specification.

As a general piece of advice, always generate a complete specification for any project - and make sure the client approves it in writing. That way you can prove you met the client's requirements, and any omission or error is not your liability.