A retroactive date is normally the date from which the insured had held uninterrupted professional indemnity insurance policy. The retroactive date is applied to all professional indemnity insurance policies and its objective is to prevent any claims arising from work done prior to date shown on the professional indemnity insurance policy.
As a result, if the policyholder had held professional indemnity insurance uninterrupted (with taking any breaks in the duration of the cover) since the begging of the contract, then the coverage may be offered for the work done in the past even if there was a switch in the insurance company.
However, there was a duration of time when the policyholder did not hold professional indemnity insurance. It means if the policy was cancelled following the end of the contract or the policy was not renewed on expiry) then the coverage of the past work done will not be covered in the new insurance policy. Hence the insured needs to ensure there is no gap in the insurance period to ensure inclusion of retroactive date in the insurance policy to get coverage for past work done.