Rule 1450 The presumptions established by this article are presumptions affecting the burden of producing evidence.

When a presumption "affects the burden of producing evidence," it means one side gets a head start. The court will assume something is true unless the other side brings forward evidence to show otherwise.

For example, if a presumption says a letter was received after it was mailed, the other side has to produce some evidence to challenge that. If they don't bring any evidence, the court will treat the presumption as fact.

This type of presumption is weaker than others in California law. It only requires the other side to produce some evidence, not to fully prove the opposite is true. Once they do that, the presumption goes away and the case moves forward normally.