Stripe error - nothing to invoice for subscription

Hi

I have an app that is sold to businesses.

Each user belongs to a business, and the subscription is held at the business level.

In stripe this means I have subscriptions with quantities of anywhere from 5 upwards.

When a business signs up to the app and pays, they choose the number of seats to purchase and can choose between monthly and annual billing.

Once the account is subscribed, and additional users need to be added, the workflow i run is:

  • Update a subscription
  • Create an invoice
  • Pay an invoice

For some accounts this process works, but for others, it throws an error as noted in the subject: Stripe error - nothing to invoice for subscription.

There clearly is something to invoice as the subscription quantity has just increased by 1.

What i am trying to achieve, is to update the subscription quantity by 1, and then take immediate payment for that “1” but maintain the current billing cycle. This means i get paid straight away for the additional user.

Not such a big deal for monthly billing but if an account has chosen annual billing, I want to get the money through the door.

As an example:
Subscription created with quantity of 4 users on 1 june 23 therefore next invoice (payday) scheduled for 31 May 24

New user added on 1 july 23

I want to invoice (one off) for time remaining between 1 july 23 and 31 May 24 without impacting the scheduled invoice for 31 may 24.

Can anyone provide any guidance as to what i should be doing/what i am not doing/ what i am doing wrong please?

Thanks
Robbie