In most cases the trim can be left on and we can sand up to it without any trouble. A few exceptions to this however, are when we are using a pigmented stain because it will transfer to the trim. Another reason we may remove it is if the trim is eventually being replaced. If the trim profile changes after we’ve sanded, the un-sanded lumber will be exposed unless we sand underneath it. Please let us know if you’d like a quote for that service. We have more information on sensitive trim here.