What is bonding capacity?
Bonding capacity is the maximum value of bonded work a surety will support, expressed both as a single-job limit and an aggregate program limit. It is an underwriting judgment based on working capital, equity, track record and the reliability of your financial reporting.
What underwriters actually weigh
Capacity is not a formula, but the inputs are consistent:
Working capital. Current assets less current liabilities, with illiquid items like aged retainage and underbilling discounted. This is usually the binding constraint.
Equity and its trend. Retained earnings growing steadily reads very differently from equity flat across three years of rising revenue.
Track record. Completed jobs of similar size and type, finishing near their reported margin.
The reliability of your reporting. The least quantifiable and often the most decisive. An underwriter who has watched three of your jobs fade will discount what you submit next, regardless of what the ratios say.
Character and continuity. Who runs the business, and what happens to it if they stop.
How it gets constrained without anyone noticing
Capacity rarely fails dramatically. It stops growing.
A business increasing revenue 20% a year while its single-job limit stays flat is being constrained, and the usual cause is not profitability but reporting: a climbing underbilling balance, a pattern of fade, or schedules that have to be restated.
The dangerous part is the timing. Most contractors discover the constraint the day they ask to increase their limit for a job they want to bid, and by then the underlying pattern has been building for several quarters. There is nothing to be done before the bid deadline.
Raising it
The levers that work are unglamorous. Retain earnings rather than distributing them. Collect retainage on finished jobs. Get change orders approved before the work is done rather than after. Update cost to complete monthly so schedules stop being restated.
All of those improve the numbers. Collectively they do something more valuable, which is make your reporting believable.
Going deeper: How unapproved change orders quietly cap your bonding capacity