You mean an ACH transaction processing system? Zenpayroll has a nice series of blog posts: http://engineering.gusto.com/how-ach-works-a-developer-perspective-pa

You mean an ACH transaction processing system? Zenpayroll has a nice series of blog posts: http://engineering.gusto.com/how-ach-works-a-developer-perspective-part-1/ http://engineering.gusto.com/how-ach-works-a-developer-persp... http://engineering.gusto.com/how-ach-works-a-developer-perspective-part-2/ http://engineering.gusto.com/how-ach-works-a-developer-persp... http://engineering.gusto.com/how-ach-works-a-developer-perspective-part-3/ http://engineering.gusto.com/how-ach-works-a-developer-persp... http://engineering.gusto.com/how-ach-works-a-developer-perspective-part-4/ http://engineering.gusto.com/how-ach-works-a-developer-persp...