The antonyms for the term "taking effect" may vary depending on the context. One of the most common antonyms for this phrase can be "ineffective", implying that something has failed to produce a desirable or intended outcome. Another antonym for "taking effect" could be "delayed" or "postponed," indicating that an action or condition has not yet come into force. Similarly, "reversed" or "cancelled" can be considered as antonyms for "taking effect," suggesting that something has been undone or negated. In contrast, terms like "inefficient," "inept," and "incompetent" can be used to denote the lack of effectiveness, making them relevant antonyms for "taking effect" in certain situations.