Errors from the API when creating invoice emails

We use your API nightly, to add invoices and to email our customers.

Last night, we received errors from 6 of these invoices - but I don’t know why they failed, only that they retuned a 400 bad request response.

Here are the details:

Failing call - /invoices/{id}/send_email

First call - 6th March, 7:00am,
Second call - Just one second later for a different invoice

We re-tried the calls with exponential backoffs, so I don’t think it was rate limiting issue?

Can someone take a look for us?


Apologies - this looks like a problem with the app in general, when i bring up the offending invoice in the web app and click “mark as sent”, I get an error “Unable to mark as sent” - and no further information.

So I think this is best handled via customer support…


Hi Matt,

I’ve just spoken my colleague and I can see that the issue has already been traced to having two invoices with the same reference number.

Glad we were able to get this solved for you.

Dave J