Additional Premium

Additional premium (often abbreviated "AP") is money an insurer bills you after the policy is already in force, because something changed that raised the price. The two most common triggers are a year-end premium audit that finds your actual payroll or sales came in higher than the estimate the policy was built on, and a mid-term change — adding a vehicle, a location, a higher limit, or an endorsement — that increases the exposure or coverage. In both cases the insurer recalculates and sends a supplemental bill.

For a small business this is the classic "surprise invoice" scenario, and it is worth planning for. On auditable policies, the deposit premium you paid up front is only an estimate; if your business grew, the audit will collect the gap as additional premium. The larger the gap between projected and actual exposure basis, the larger the bill. Growing companies routinely owe additional premium simply because they hired staff or booked more revenue than they forecast at the start of the term.

The practical nuance is timing and avoidability. Additional premium from an audit is due after the term ends, which can strain cash flow if you have not reserved for it — so update your exposure estimates with your agent mid-year if your business is expanding. Additional premium from a mid-term change, by contrast, is usually prorated for the remaining days of the policy. Either way, additional premium is not a penalty; it is the correct price for risk you actually carried but had not yet paid for.