What is included in the contingency line for a commercial estimate?

Contingency in a commercial estimate covers latent soil issues, mid-project design changes and the kind of variation that arises on almost every real construction site, similar in principle to residential contingency but often set at a level appropriate to the larger scale and complexity of commercial work. It should remain a visible, separate line in your proposal rather than folded silently into a headline rate. Spending contingency early on upgrades leaves less buffer for a genuine site issue discovered later in the programme.