When we transfer a $5 API balance, our monthly usage limit becomes $100. So, once the $5 is used up, do we need to transfer any more balance? Or do we need to pay the usage amount again at the beginning of the month?
You will need to have a prepaid account organization positive balance in order to pay for API services. Pay-per-use API calls are deducted from your current credit balance. Review pricing to see the expense of using each model, by the amount of input and output data consumed.
The monthly limit resets at the start of every month; it does not have a sliding window.
However, if you make a few regular smaller payments, and your latest payment is over 7 days since the initial one, and the total you have paid to OpenAI becomes over $50 at that time, you will be elevated to tier 2, where both the monthly limit and the rate limits per minute and per request will be lifted higher. Thus, the monthly limit is increased before it becomes a concern, just with a slowdown to prevent immediate high-value fraud.
It is the relatively low token-per-minute limit at tier-1 that is the largest concern, blocking you from making a single AI call if you try to use more than 30000 tokens of input on a non-mini model (or by a model’s iterative tool calling.)