Normally, our company (in the US) announces pay raises in January. Last year, however, most of the people in my company did not receive a pay raise.
I'm an engineer, and even before this, I was petitioning for higher pay, based on my experience, knowledge, etc. The company agreed, and I was one of a few that did receive a pay raise that year.
However, I wasn't told about it until May. My manager sat down with me, and gave me a copy of the payroll change notification that was going to HR. This paper was signed by the CEO and my manager (signatures dated in May), and the effective date of the increase was a date in February.
I wanted to celebrate, and got permission from my wife to buy an expensive hobby item, which worked out to approximately the amount of back pay I was expecting on my next pay check (signed by the CEO!).
However, when I got my check, there was very little back pay (only a couple weeks worth). I brought this up to my boss, who promised to look into it. He admitted that it was a mistake, and that the forms were dated when the normal pay raises were supposed to be announced and he forgot to change it. When I pushed back, he said something along the lines of "If you want the money, I can pay it out of my pocket, it's my fault and not the company's."
Today, I asked HR for a copy of the pay raise notification (I have a copy somewhere at home). When HR pulled out the form, there were a couple other versions stapled to it - these were corrected forms that had an effective date of just a couple weeks prior. I have never seen these forms until today.
Of course, I'm not asking strangers on the internet legal advice ... I'm trying to get a feel on whether I should press this issue with my company or not.
Is my company legally obligated to pay me this money
You're not going to get that answer here which is probably why you were downvoted (and probably will be some more). This is not something a typical HR specialist or generalist could answer. It's not about navigating the workplace it's about "is my employer breaking the law". Get a lawyer. I'll add however that people are allowed to make a mistake. Nobody broke a contract. He filled out the paperwork wrong. If he put an extra zero on that paper, would you expect that too? They made a mistake and they corrected. Poo happens. – Chris E Aug 15 '17 at 14:39