The procedure can vary greatly from court to court, and even among different judges in the same court.
The Legislature allows judges to give certain drivers one deferred finding on a moving violation (like a speeding infraction) and one deferred finding on a nonmoving violation (for example, an expired tabs infraction) in a period of 7 years. However, there is no requirement under Washington law that judges grant deferred findings; rather, judges have discretion. Some judges don't grant deferred findings and other judges only grant deferred findings in limited types of cases and all judges are prohibited by the Legislature from granting deferred findings in specific types of cases.
By taking a deferred finding, the respondent is allowing the police officer's report to be used against the respondent should the respondent fail to meet certain conditions. The conditions vary from court to court, but at a minimum there is usually some payment of an assessment (which could be higher or lower than the amount written on the ticket), and often a period of deferral, which can be up to a year with no new infractions. At the end of the deferral period, if the respondent has met all the conditions, the court will dismiss the ticket.
Because procedures vary greatly among different courts, it is best to seek out an attorney to determine your eligibility. A deferred finding should be used sparingly and it is better if a person is able to get a ticket dismissed rather than deferred, although on special occasions a deferred finding can make financial sense.