E&O is written on a claims-made basis, which means coverage responds to claims first made against you during the policy period — even if the work happened years earlier — as long as the work occurred after the policy’s retroactive date. By contrast, occurrence-based policies (which is how GL is usually written) respond based on when the injury occurred, regardless of when the claim is reported. Claims-made matters in two specific situations: (1) switching carriers — your new carrier must accept your original retroactive date or you lose coverage for old work; (2) discontinuing coverage — you need tail coverage to maintain protection for work done while insured. We manage both transitions carefully.