Can I reuse a module’s FCC and ISED certifications in my finished product without any testing?

Sometimes, but only if you do not change the RF conditions on which the certifications were based. Modular approvals cover the radio module itself under specific assumptions about antenna configuration, RF exposure conditions, operating modes, and integration constraints. Once the module is installed in a host device, the final product becomes the regulated object. If the enclosure, grounding, antenna placement, cable routing, duty cycle, or co-located radios materially change radiated behavior or RF exposure, the original approvals no longer stand on their own. At a minimum, you must perform a technical assessment to confirm continued compliance. In many real products, some level of host-level verification testing is unavoidable.