Even if a laboratory only uses standard published methods accreditation bodies will require it to generate data to substantiate the validity of claims being made about the bias (accuracy), precision and, if relevant, limit of detection of methods. For most accreditations it will be up to the laboratory to determine, in consultation with its customers, what levels of performance are appropriate. In other instances, for example UK MCERTS accreditation, the accreditation scheme may specify a minimum level of performance required before accreditation can be granted.
Although not a direct part of many accreditation standards accreditation bodies will typically have protocols which they regard as a suitable approach to method validation and processing of the resulting data.
We can advise you on what approach is suitable to satisfy your accreditation body for your discipline. This will include preparation of suitable validation protocols and assistance with processing the resulting data.