There's something of a tension in canon in this regard. On the one hand, we have seen only very limited examples of "tracking magic" available to the Ministry. The Trace, which is limited to kids, and (possibly) the Taboo, which is limited to specific words. Other than that, the only example I can think of is Fantastic Beasts 1, the map of New York which shows where powerful magic is being cast. We also know that you can't track apparition unless you physically grab the person. So on that front, you'd think the Ministry would have limited ability to monitor magic around the country. On the other hand, you have the fact that wizarding Britain seems to be a fairly lawful place, where wizarding law enforcement is (generally) quite effective. Azkaban is full of captured criminals. If the Ministry really was as limited as the above suggests, how would they ever catch any criminals at all? Magic provides so many ways to get away with crimes, surely there must be some powerful tracking/monitoring magic that the Ministry has access to. Similarly, the continued effectiveness of the Statute of Secrecy would, you'd think, require an ability to monitor magic cast in Muggle locations. There are also some parts of canon which are quite plot holey unless you assume the Ministry has a high level of monitoring ability. For example, in DH when they are camping and complaining about having shitty food, the question is: why not go to a random Muggle town and buy (or steal) some nicer food? It would be so easy. The only real reason they wouldn't is if they couldn't, which suggests that if they had gone into a random Muggle town the Ministry would have known very quickly. So: 1. What is your preferred balance of the Ministry's ability to track magic vs. individuals' ability to cast magic in private? 2. What are some interesting ways you can think of by which the Ministry could monitor magic? One avenue I like for question 2 is animals - the Ministry had the ability to know about any magic cast in front of animals, that would give a significant but gameable monitoring ability to the Ministry.