open thread – April 14-15, 2023 — Ask a Manager

I have several years of experience as a clerk at my workplace, and last year, I was promoted to assistant manager.
A few months in, I found out that per hour, I made less than the new hourly clerks, who were all hired shortly after I was promoted.
Apparently, it wasn’t intentional, and my boss brought the discrepancy to her boss’s attention a few weeks after I was promoted. He said my benefits make up for it, so he wasn’t going to adjust it. So, she didn’t tell me what the clerks were making. In addition, she took on payroll and scheduling, which were supposed to be my tasks, in an effort to hide it. I believe she was even doing it from home.
I eventually found out from the clerks what they were making, but I didn’t say anything. When I finally had the guts to ask about it, I was told that the grandboss’s reasoning is that my benefits make up for it, and my boss invited me to talk to him about it.
I mean, even though I have benefits, I still think I should have been making at least as much as the people I supervise, if not more, especially since I had several years of experience that they didn’t have. But even so, upon consulting with a former manager, I learned that even with benefits, the assistants have always made more than the clerks (clerking used to be a minimum-wage job, so they would have to). Also, when a colleague was promoted to interim assistant manager for a few months pre-COVID, I know for a fact he was offered a dollar more per hour.
That’s a horrible position for a manager to be in, of course. Still, I’m astounded at the fact that she went out of her way to hide it for months on end, and to her detriment. She was constantly overworked. And of course, as soon as I told her I knew, I was finally taught how to do payroll and scheduling. I did eventually get a raise, but this whole thing really affected my trust. None of the new hires have been making as little as I was, and I’m one of the few people at my level who have been here for more than five years (and the only one in my department who has been here more than two). In fact, it’s become quite evident in the past few weeks that they’d be really stuck at this time of year if I wasn’t still working there.
I know she’s not the problem here–obviously, she didn’t decide to pay me less. That said, to me, there was a certain lack of integrity on her part. I like to think that if it was me, I would’ve been direct with my employees–but that’s easy to say if I’ve never been in that situation. All in all, it really hurt me, and I’m still wondering about asking for back pay.
What do you think? Am I right to put any blame on my boss here? Would she have even been able to tell me what was happening?
Also, if asking for back pay is a good idea, how much should I ask for? Just enough to catch up to what the clerks made? Or that plus a dollar more, like previous assistants made?