What a loss run contains
Each claim is typically listed with its date of loss, description, amounts paid and reserved, total incurred and open or closed status. A loss run with no claims still matters, because it confirms a clean period.
Why underwriters need it
Underwriters use loss runs to judge how a risk has performed, so a commercial submission without current loss runs is usually treated as incomplete. Brokers request them from each prior carrier, which can mean several requests and formats.
Why they are hard to work with
Every carrier formats loss runs differently, many arrive as scanned PDFs and the same claim can show different values on reports a few months apart. Summarizing them into a loss history is careful, manual work.
Where automation helps
Loss runs can be read automatically into one structure, deduplicated across reports and summarized by year and line of coverage. Good systems also link every figure to its source page, since underwriters check the large losses themselves.