Recently the Arizona Legislature enacted a new and shorter statute of limitations for UM/UIM claims. The applicable section is ARS 12-555.
For uninsured motorist (UM) claims such claims, such claims must be made in writing within three years after the earliest of (i) the date you knew that the tortfeasor was uninsured; or (ii) the date you knows or should have known that coverage was denied by the tortfeasor's insurer; or (iii) the date you know or should have known of the insolvency of the tortfeasor's insurer.
For underinsured motorist (UIM) claims such claims, such claims must be made in writing within three years after (i) the date you filed a timely action against the tortfeasor; or (ii) the date you know or should have known that the tortfeasor has insufficient liability insurance to cover your injuries.
Moreover, if a settlement is not reached, you must request arbitration or file suit pursuant to the terms of the insurance contract within three years after providing the written notice described above.