Difference between actual duties and prima facie duties?

"According to W. D. Ross (1877-1971), there are several prima facie duties that we can use to determine what, concretely, we ought to do. A prima facie duty is a duty that is binding (obligatory) other things equal, that is, unless it is overridden or trumped by another duty or duties. Another way of putting it is that where there is a prima facie duty to do something, there is at least a fairly strong presumption in favor of doing it. An example of a prima facie duty is the duty to keep promises. "Unless stronger moral considerations override, one ought to keep a promise made."

By contrast with prima facie duties, our actual or concrete duty is the duty we should perform in the particular situation of choice. Whatever one's actual duty is, one is morally bound to perform it. Prima facie duties relate to actual duties as reasons do to conclusions of reasoning.

Note: The term "duty" in "prima facie duty" is slightly misleading. The prima facie duties are understood as guidelines, not rules without exception. If an action does not correspond to a specific guideline, one is not necessarily violating a rule that one ought to follow. However, not following the rule one ought to follow in a particular case is failing to do one's (actual) duty. In such cases it makes sense to talk about violating a rule. The rule might be the same in Words as a prima facie duty (minus the phrase "unless other moral considerations override"), but it would no longer be merely a guideline because it describes what one concretely should do."