As we discussed About Plans in a previous article, you can add credits to your plan as you go at any moment in time.
Credits are used in e-satisfaction to count the number of responses that you get for each application.
A credit is used whenever an end-user submits at least one response to their questionnaire.
When you run out of credits, all mechanisms that send questionnaires to the end-users stop. This means that Pipelines will stop sending queue items (queue items will get a different status) and public links will display the "Thank you Page" directly.
Normally, as mentioned before, credits are used when the user submits at least one response. However, there are times when a user receives a questionnaire (through a channel like Email or SMS) and hasn't responded yet. Having this in mind, credits might reach 0 but there are still some questionnaires pending out there. In this case, credits will simply get negative values.
This will not affect your plan in any way and your credits will be renewed, to their initial value as scheduled.
As described in the Plan article, Plans can be of 2 durations:
Once Off (no expiration)
Monthly
During once-off plans, the credits you acquire are meant to last forever, meaning that they will not be renewed, unless new credits are purchased.
For monthly plans, your credits will be renewed every 30 days, according to the plan starting date.
NOTE: If credits < 0, they will be renewed to the initial value without any other reductions.
NOTE 2: If there are still left credits into your account, they are lost.
At any moment you can purchase extra credits for your account so that you can receive more feedback.
Extra credits have the same duration as the normal credits and they are not renewed.
In all cases, the extra credits will be used first and then the normal ones. This means that if the plan is renewed and the credits are renewed as well, the extra credits will still be consumed first.