The action agency may reach a “no effect” conclusion if it determines the proposed action will not affect listed species or designated critical habitat. The action agency may reach a “not likely to adversely affect” decision if the proposed action is insignificant or beneficial. The Services will then review the biological assessment and either agree or disagree with the agency's findings. If the Services agree the project's potential impacts have been eliminated, they will concur in writing. The concurrence letter must outline any modifications agreed to during informal consultation. If an agreement cannot be reached, the Services advise the action agency to initiate formal consultation.