Contingency

A contingency is a percent added to a job's costs for surprises: rot behind the siding, a slow inspector, a week of rain. Big jobs are where surprises cost the most. 5 to 10% is common.

Set it on an estimate under Equipment and other costs. It's added to job costs, so the price covers it.

Once two or more jobs are closed, the job page shows what share of costs your jobs didn't plan for, with a Use button that makes it the contingency every new estimate starts with. Reports show the same number. You can also set it in Company settings → Work rates and extras.