Professional firms always want a single number for E&O, and it never comes that cleanly. The premium is assembled from your exposure and your history.
What mostly sets the price
The biggest drivers come with the work. Your profession matters: a tax preparer, an IT consultant, and a marketing agency carry very different risk. Your revenue scales the premium. The specific services you offer, especially higher-risk advisory or technical work, shape it. And the limits your clients require, often one or two million, set the rest.
What you can influence
Several drivers respond to you. An accurate scope of services keeps you from overpaying for work you do not do, or being underinsured for work you do. A clean claims history follows you and lowers cost over time. Deductible and limit choices trade premium for retained risk. And because we are independent, shopping the market finds the carrier that prices your specific profession best.
The quiet overcharges and gaps
The issues we find most often are mismatches. A policy describing services far broader, or narrower, than the firm actually offers. Limits carried over from a smaller version of the business, or below what current contracts require. Duplicate coverage across overlapping policies. These are invisible until someone matches the policy to the real firm.
What not to do
The tempting mistake is buying the cheapest E&O with a scope that does not match your services, then discovering at claim time that the work was outside the described services. A low price on coverage that does not fit your firm is the most expensive insurance there is.
A coverage review checks both sides: that you are not overpaying through a mismatch, and that the scope and limits actually fit your services and contracts.