2. Adjudication, Informal
agency action
Informal adjudication is an ill defined but broad category of agency action.  The APA's do not specifically define informal adjudication.  A working definition of informal adjudication is that it is a statutorily required decisionmaking process that may or may not require a hearing and is neither formal adjudication nor rulemaking.  If the process does not involve formal adjudication or rulemaking, it may come under the default heading of informal adjudication.  The decisionmaking process is more likely to be defined in the agency organic legislation than in the APA, but the scope of judicial review is usually found in the APA.  The Federal Overton Park case is the initial source for identifying a number of the characteristics of the informal adjudication.  There are vastly more decisions made in informal adjudications than in formal adjudications.
hearing
Informal adjudication may or may not require a hearing process as part of the decisional process.  If a hearing is required, it will not be a closed record, adversarial hearing as used in formal adjudication.  If a hearing is required, it may or may not be an oral hearing.  The statute authorizing the decisional process is the first place to look for any hearing requirements.
judicial review
The decision in an informal adjudication will usually be subject to judicial review.  The Federal Overton Park case illustrates one level of judicial review.  The organic statute of the agency that delegates the decisionmaking authority to the agency will be the first place to look for judicial review elements.  In the federal system, the informal adjudication may be reviewed under the broad category of "agency action."  In a state APA, the scope of review may be patched together by considering the factual, legal, and other components of the decision.
procedure
The procedure used in informal adjudication decisionmaking is most likely to be found in the organic legislation authorizing the decision.  The prescribed procedures may be implicit or explicit.  The prescribed procedures are likely to vary greatly from one statute to the next.
record
The informal adjudication decision must be based on a record, although it is not the closed record that is required in formal adjudication.  A record is required either because of the terms of organic statute or because otherwise the court will have no basis for judicial review in the absence of a record.  The record may consist of the agency order, any public submissions, agency studies or investigations, or any matters considered by the agency.  The record on review cannot be based on post hoc rationalizations.