How can I generate an immediate charge for a subscription?

You will either need to change the subscription's next bill date to a sooner date and time by going to options, view subscription then, "change" in the subscription table of the account or create a one-time charge to generate an invoice to collect the payment. If you use the one-time charge option you will also need to apply a credit or coupon to the account to cover the cost of the next renewal for the subscription. The process of applying a credit or coupon to the account is so that your client is not billed twice for the subscription payment when it renews, since you have already collected the payment using a one-time charge.

Otherwise, the charge does not exist until the renewal date.