Please inform the user. It is called "being nice" even though you probably are not legally bound to. In fact, you could very well be within your terms to charge

Please inform the user. It is called "being nice" even though you probably are not legally bound to. In fact, you could very well be within your terms to charge them because that's what free trials are for right ? If I was that user and you sent me the email, I will do these things: 1. Be really happy that you informed me. 2. Cancel my subscription if i really don't need your service. Renew it *happily* if I want your service. But the most important thing that will happen is that I will remember you/your company that you employ good practice. If it comes down to choosing b/w you and someone else and the difference is marginal, guess who will I choose ? If a friend asks me for a service similar to yours, guess who will I recommend ? Happy customers (even ex-customer) can help you in many ways even if they are not paying you. Now, let's look at the other side of it. If you do not email me, you will make some money from me in the short term. But I will ensure that I remember you for the wrong reasons. I will also ensure that if someone asks me about you, I will tell them to stay away. Heck, if I really took it personally, I will even write a hate blog and submit it on HN. Imagine the PR issues you could potentially have. So be nice and it always comes back to help you. Even if you are not making money from a user in the short term, who knows that user might be able to help you indirectly in securing a lot more users who will pay. May be.