This seems like such a simple question, but I'm hoping someone who has purchased an SPSS subscription add-on might be able to provide some insight. I have a base subscription already. I need the custom tables add-on. When I try to purchase the add-on via my IBM account, it adds a charge for the base subscription again. I can't remove this charge. When I get to the payment page, there is a prorater charge for the add-on (i.e. it reduces the amount to pay based on the subscription period left in the current cycle); however, it doesn't add a prorater credit for the base subscription that I've already paid. I've had a frustrating couple of days cycling through IBM support options with no resolution. I can't even work out what the right charge should be; an "add-on" to me implies that you have the base subscription and you can add/remove modules separately to this, but maybe this is not the case. To get the add-on do you always have to purchase another base product (so it's not really an "add-on", it's just a different SPSS product)?