One score, out of 100, applied identically to every broker. It is shown out of ten on this site because that reads more naturally beside a comparison - the underlying number is the same one our other sites use.
Bonuses and sign-up offers carry no weight. They change monthly, they are usually conditional on volume, and rating them would reward marketing spend rather than trading conditions.
Each broker's own published material in the first instance, with the source recorded on the review page. Brokers are shown their review before we treat it as settled, and corrections are made on evidence, not on request.
Some brokers pay us a commission when a reader opens an account through our link. That has no bearing on the score - the measures above are applied the same way to brokers who pay us and brokers who do not, and several of the brokers listed here have no commercial relationship with us at all.