If you make requests too quickly you will receive a 429 Too Many Requests error. Each response from daisyBill includes headers pertaining to your rate limit, including the limit, the remaining number of requests, and the time at which the limit will reset. See below:
X-Rate-Limit-Limit:100
X-Rate-Limit-Remaining:99
X-Rate-Limit-Reset:2017-04-12 10:01:00 -0700