[rs]

You should send a reminder, even if it's just a few days before you take the charge. It's not just a Good Thing To Do, but it will even reduce the risk of charge-backs.

As your business grows and you take on more payments, you will find there are a small group of your customers who will look at their credit card bill at the end of the month (or months) and just call up the credit card company to charge back items that they don't recognise (due to them not recognising the charge (innocent mistake) or they genuinely didn't use your service and feel "cheated")

On a side note, why do you take CC info at signup ? I've done about 4 SaaS currently live, and not a single one takes CC information upfront, but rather send them a reminder to pay an invoice as their trial reaches it's end.