I’m getting a 503 response code error when doing a bulk upload from FileMaker to Xero.

An HTTP 503 response usually means “Rate Limit Exceeded”.

An application can make up to 5000 API calls against a particular Xero organisation in a rolling 24 hour period and 60 calls against a particular Xero organisation in a rolling 60 second period. The following will be returned in the body if you exceed a rate limit:

oauth_problem=rate%20limit%20exceeded&oauth_problem_advice=please%20wait%20before%20retrying%20the%20xero%20api

(unencoded this is “oauth_problem=rate limit exceeded&oauth_problem_advice=please wait before retrying the xero api”)

The most common issue encountered is the 60 requests/min rate limit. If you’re encountering this limit simply add a pause of a few seconds to your looping script to keep the upload within the allowed limits

You can get more information about Xero API Rate Limits here:

https://developer.xero.com/documentation/auth-and-limits/xero-api-limits