Let's say customer have an account, for which he paid for an year (with discounts you offered him for an year).
And after few months he wishes to upgrade his account.

How much he should pay? (considered that he bought account with discounts, and has used some of it)

Asuming the customer already used 2 months of hosting and payed $ 100.-


1. Agree to a price per year for the upgraded account, including discounts you want to give etc. (lets say $ 200.-

Since there is only 10 months left in the year, he only has to pay 10/12th of 200.- is $ 166.67

2. Since he already payed you $ 100.- you deduct this amount. But only 10/12th of it because he already used up 2 months.
Used up: $ 16.67, amount left 83.33

So he pays you 166.67 - 83.33 = $ 83.34 extra for the remaining 10 months.

He has now paid 2 months hosting at $ 100.- per year
10 months hosting at $ 200.- per year

Originally posted by Pilgrim
Asuming the customer already used 2 months of hosting and payed $ 100.-


1. Agree to a price per year for the upgraded account, including discounts you want to give etc. (lets say $ 200.-

Since there is only 10 months left in the year, he only has to pay 10/12th of 200.- is $ 166.67


Thank you Pilgrim, nice calculations :)

You propose here to give him 1 year discounts for 10 months (I mean same %).
But if I have expenses for payment methods, then I loose some money, because payments will be made more than once/year (if user will decide to made one more upgrade it could be worse)

I not complying here, I’m just looking for a better solution :)

Add the cost of billing to the fictional amount of $ 83.34?

If you're that concerned about transaction costs, you may want to look into a better billing system.