When a contractor finds work the carrier's estimate didn't cover, they submit a supplement — a documented request to increase the settlement. Used honestly, it's how real, hidden damage gets paid for. Used loosely, it's how a low bid becomes a moving target.
The legitimate kind
Xactimate estimates are built fast and routinely undercount — a supplement for genuinely discovered damage (behind a wall, under flooring) with photos and documentation is normal and expected.
The red-flag kind
A bid full of 'pending inspection' and 'supplement to follow' language is telling you the final number isn't real yet. That's supplement risk — the contractor books the job low, then re-opens the claim mid-project when you have no leverage.
BidsScores scores supplement risk on insurance bids so you can favor the contractor whose number will actually hold. See also our guide on why a bid can come in higher than the carrier estimate.