jQuery Form Submit fails?

Cheeky Jquery fails to auto submit forms sometimes and this is due to the submit button interferring with the .submit(). call.

I found this out when creating an autologin feature for a client. They needed to get username details from clients on their own website, check for authenticity and then if OK create an autologin token and redirect to the suppliers website via a post form.

Everything was going OK until the point of automatic form submission when it failed with the error Property 'submit' of object # is not a function.

This was the JQuery

$(document).ready(function(){
  $('#clientform').submit();
});

and the HTML:

but apparently according to Jason on StackExchange:

and what a result, changed the HTML and it works: