Subsidy margin determination for non-investigated exporters allows periodical review and possible retrospective countervailing duty with provisional guarantees permitted. Rule 23A requires the designated authority to conduct periodical reviews to determine individual subsidy margins for exporters or producers not investigated previously, where they show they are unrelated to investigated parties. During the review period, the Central Government will not impose countervailing duties on imports from those exporters, although provisional assessment and guarantees may be applied on the authority's recommendation; if a subsidy is later found, duty may be levied retrospectively from the review's initiation. Duties already applied to cooperative un-sampled exporters may be extended to previously uninvestigated exporters.