The debate is usually conducted as a matter of philosophy — alignment of incentives versus predictability of cost. Both arguments are real, but they obscure that for any given practice the comparison is arithmetic.
What each model actually charges for
A percentage charges for outcome. If a claim never pays, it costs nothing. That genuinely aligns the biller with the practice on denials, because unworked denials cost the biller too.
A flat fee charges for capacity. The cost is the same in a strong month and a weak one, which makes budgeting straightforward and means a good month is not taxed.
Where they diverge
At low volumes, a percentage is usually cheaper — and can be so cheap that it does not cover the work, which is why any serious percentage arrangement carries a monthly minimum. A practice collecting $8,000 a month at 7% pays $560, which does not fund a competent revenue cycle. If there is no floor in the contract, ask what is being cut.
At high volumes the relationship inverts. A percentage scales without limit while the work does not scale proportionally — a practice collecting $2m a month is not creating twenty times the claims work of one collecting $100,000. This is why large groups negotiate percentages down, and why at sufficient scale a flat arrangement is simply cheaper.
Payer mix matters as much as volume. A book of high-value, low-count claims is less work per dollar than a book of low-value, high-count ones. Two practices with identical collections can require very different effort, which is why a rate quoted without any question about payer mix is a guess.
The part that is not a preference
In some states the choice is not yours or the vendor's. Several restrict or prohibit compensating a billing company as a percentage of what it collects, and in those states a flat arrangement is the only available structure. Where that applies, the useful question is not which model you prefer but whether the flat fee has been set to land in the same place the percentage would have.
Run the comparison on your own numbers before the conversation: annual collections times the offered percentage, against the annual flat quote plus any per-unit add-ons. It usually takes ten minutes and it removes most of the debate.
Denials Piling Up?
We handle the revenue cycle end to end — coding by certified coders, claim submission, denial management and appeals, and A/R follow-up, with six reported numbers every month.