Counter-foils are typically used to verify the authenticity of a document or to keep track of a business transaction. However, it is essential to understand the meaning of its antonyms to use it correctly. One of the antonyms for the word counter-foils is "original," which refers to the primary document or the first version of it. Another antonym is "fraudulent," which means fake or not genuine, commonly used in the context of counterfeiting money. Lastly, "inaccurate" is the opposite of counter-foils, which means false or incorrect. Knowing these antonyms will help you differentiate between a legitimate copy and a potentially fraudulent one, ensuring the security of your documents.