What is the difference between occurrence and claims-made for tower work?

Occurrence policies cover claims arising from incidents that happen during the policy period, regardless of when the claim is filed. Claims-made policies cover claims that are both made and reported during the policy period. For tower contractors, occurrence is strongly preferred for GL and umbrella because latent injury claims (such as a structural failure discovered years later, or delayed-onset health effects from RF exposure) may not surface until years after the work. Claims-made creates gaps if coverage lapses or is not renewed. Most MSAs require occurrence-form GL. Claims-made is more common for professional liability and pollution, where tail coverage handles the gap. If you are forced into a claims-made GL due to market availability, you must understand the retroactive date (claims from incidents before this date are excluded) and the need to purchase an extended reporting period (tail) if you ever cancel or non-renew the policy. Without tail coverage, claims reported after cancellation are uninsured even if the incident occurred during the policy period. For a tower contractor, this could mean a structural failure claim surfacing two years after you completed the work would be denied.