The subpoena goes to a private accounting firm. They won’t refuse to comply. They would be insane to. Trump needs to get an emergency stay like tonight from a higher court or by the time it makes it way up, the Dems will have the records.
CPA firms are often in a difficult position and their counsel would likely advise them to comply. But they can certainly buy enough time to let the President’s counsel request a stay and appeal. After all, Trump has financial interests in numerous entities, including LLCs and partnerships. He also has co-investors, members, and partners whose confidentiality would be compromised by compliance. They need to come to his assistance post haste for their own protection especially from Congressional staffers leaking their private business to the media.