This means that you cannot get paid twice for the same damage or injury! or can you?
Non Duplication of Benefits clause explains that if an insured receives payment for damages from any source, then he/she will not be entitled to payment by his own insurance company. The opposite situation also applies, If an injured person receives compensation for the injury, from a source independent of the responsible party (his or her own insurance) then the responsible will have to pay the insurance company.
A similar circumstance occurs with the collateral source rule: a rule of evidence that prohibits the admission at trial of evidence that a victim's damages were compensated from some other source of compensation (insurance companies). For example, in a personal injury action, evidence that the Plaintiff's medical bills were paid by medical insurance is not admissible.
If this rules is not in effect in your state, then payments by insurance companies (even you own) can be considered by a jury, in which case you can receive a reduced amount.
Non Duplication of Benefits clauses are illegal in Arizona and Montana. If you get in an accident in those states, the injury payments (not the damages to your car) can get paid twice. How? If you file a personal injury protection claim, and your insurance pays your doctor, then the responsible party’s insurance company will have to pay you AGAIN for those payments.
Why? Because State Law in those states have render Non-Duplication of Benefits and Subrogation of Rights Clauses invalid.