best way to deal with upgrades mid-payment

[mediakitchen]

My site involves advertisers paying for monthly advertising (on a calendar month basis) and there are 3 levels of advertising.

I would like to add the option to upgrade from one level to another and I am not sure how best to deal with charging for this if they are mid-way through the month. It would be complex to work out the additional cost on the number of days left in the month - would it not?

Ideally I would like it all automated.

Any advice appreciated!

Thanks

Paul

[ServWise]

My site involves advertisers paying for monthly advertising (on a calendar month basis) and there are 3 levels of advertising.

I would like to add the option to upgrade from one level to another and I am not sure how best to deal with charging for this if they are mid-way through the month. It would be complex to work out the additional cost on the number of days left in the month - would it not?


Complex? not really


D = Days in current month
A = Current monthly payment
N = New monthly payment
T = The current day of the month


(N - ((N / D) * (D - T)) - A = Prorate payment for time left at new rate

[ServWise]

sorry should have been

D = Days in current month
A = Current monthly payment
N = New monthly payment
T = The current day of the month

((N / D) * (D - T)) - ((A / D) * (D - T)) = Prorate payment for time left at new rate

[Peter Bowen]

Upgrade them straight away and charge them for it starting at the next month. You don't have to worry about difficult calculations and your customer gets a little more than expected.

[downsouth]

Would it be a good idea to 'offer' this upgrade mid month as a freebie, then at he start of each month collect the new higher advert charge?

Is charging people going to bring in that much more income? it may upset a few i dont know?

The only issue I see is that for people 'upgrading' just after that months payment, dropping back down, paying again, then upgrading again, but i'm sure that can be controlled.

Do you tie in your advertisers for a set period at each level?

[mediakitchen]

Thanks for the replies.

I guess it is not too complex to calculate the partial month payment.

I do prefer the option to only charge when we get to the next month however this may open some loopholes as someone could pay for the less expensive advertising package and then one day into the month upgrade to the more expensive one then at the end of month downgrade again. Don't want to have to add loads of complicated terms and conditions to deal with this.

Anyone else had to deal with a similar scenario?

Paul