how does killbill calculate prices?

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Sep 25, 2021, 4:21:08 AMSep 25
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Hi Killbill team.

I have a question about the price calculation in killbill.

I have an evergreen plan TVM-BS-326-QUARTERLY with an billing_cycle of Quarterly with a price of 783.84.

I have created an account with the tag AUTO_INVOICING_OFF
added a subscription with the plan  TVM-BS-326-QUARTERLY with a start date 2021-09-13
I then have blocked the invoicing via blocking states
block_billing 13-9-2021
unblock_billing 30-9-2021

remove tag AUTO_INVOICING_OFF from account

If i then run a invoice run(or dry run) for 30-9 I get an invoice line for  TVM-BS-326-QUARTERLY

start_date 2021-09-30
end_date 2021-12-01   
amount 534.04 DKK

Our current billing-system handles billing of monthly prices subscriptions that do not line up with months simply by assuming all months have 30 days and setting a day price by dividing the price with the months.
In this case the monthly price is

Since the period (2021-09-30 - 2021-12-01) is 62 days in our current billing-system we would calculate
62 * (261.28/30)
This adds up to

We are at the moment testing the invoices generated by kill-bill.
I have been asked to explain how the amount is calculated.
Can you help me explain how 534.04 DKK  has been calculated.

I need to explain this to my billing the department and later when killbill is production to my customers.

I would also like to know where in the code these calculations are.

I have attached a catalog and a small script to generate and account with a subscription in the above state.
I had to change the dates one year in the future to get it to work.


stephane brossier

Sep 30, 2021, 6:58:56 PMSep 30
to, Kill Bill users mailing-list
The quarterly period going from 13-9-2021 -> 13-12-2021 contains 91 days, i.e 30 (sept) + 31 (oct) +30 (nov) 
The # days you are billing for is 92 days

783.84 / 91 * 62 = 534.04

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stephane brossier

Sep 30, 2021, 6:59:52 PMSep 30
to, Kill Bill users mailing-list

> The # days you are billing for is 92 days

The # days you are billing for is 62 days

daniel nielsen

Oct 1, 2021, 4:26:04 AMOct 1
to stephane brossier, Kill Bill users mailing-list
Thank you stephane.
That makes sense.

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