Yes, the insurance can be purchased from the new insurer before the expiry of the current professional indemnity policy subject to nil claims declaration on doctor's letterhead along with proposal form for issuing the policy from the new insurer.The new insurer will issue the policy and mention the retroactive date as mentioned in the last policy issued by previous insurer. The claims arising for the previous years will be handled by the new insurer as per policy terms and conditions and sum insurted of the previous policy.