You can configure a membership to start in the future. This is often useful when migrating from another system and the user has already paid for the current month.
In this example, we are configuring a monthly membership and payment to start on April 25th with a recur date of the 25th every month going forward.
1) Click the button to change the membership Start Date (defaults to "today")
2) Click Update cart to see updated date and prorating information. In this case, there should be no prorating.
3) Take full advantage of the cart review screen, it has all the details you need to know that things are going to happen as you (or your clients) expect.