"We're very confident we're within the cap and within those financial regulations," Horner told BBC Radio 4's Today programme.
"So we've been shocked at the speculation and accusations that have been made by other teams. We wait for the FIA to conclude their process and we wait to see what comes out. Anything other than compliance we'll be extremely surprised at."
In addition to the potential of an appeal, Red Bull also have the opportunity to enter into a 'settlement agreement' with the FIA.
In this scenario, a team accepts its guilt and the FIA imposes a penalty it deems appropriate.
If a settlement agreement cannot be reached, the dispute will go to an adjudication panel of independent judges, who will look at the case and come to the conclusion whether the offence should be penalised.
If the team is still not happy after that, it can take its case to the FIA's international court of appeal.
Aston Martin did not comment, but their position is understood to be that they spent less than the total amount of the budget cap in 2021 and regret their breach, which centred on administrative protocols that reflect what they consider a complex regulatory interpretation.
Ferrari team principal Mattia Binotto said on Sunday that even a so-called 'minor' breach was a significant offence, and detailed the value of an overspend to a team's competitiveness.
Binotto said: "If there is a breach, the penalty has to be significant. Our car has been developed respecting the budget cap and we know how much even a minor breach would have implied in performance.
"$5m is about half a second, $1-2m is 0.1-0.2secs, which can be the difference between second on the grid to pole.
"It is about 2021. And also over the following seasons. I am expecting full transparency and clarity on the discussions they have had."
Mercedes F1 team principal Toto Wolff has also called for transparency about the process that was used to arrive at the assessment of any offence.
https://www.bbc.co.uk/sport/formula1/63204082