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I have been working with my current employer for about two years now. I filled in a specific niche role, which has since expanded to become an important part of our software department. I not only completed all the projects tasked to me over the year, but completed nearly an additional 50% more projects than I was tasked, with excellent results. So, I felt it prudent to request a substantial salary increase (~20%).
Unfortunately, I'm told that I already earn the maximum amount my company offers for my current role, and they can't pay more. I countered with the suggestion that if that's the case, I should be promoted, if that's what's required to advance my financial goals. The company has higher echelons of technical roles (ie: senior engineering specialist, principal engineer, etc) and less technical roles (ie: team lead, 50-50 split of technical and non-technical work, etc) that earn more than I do at my current role (senior engineer).
Being brutally honest, I plan to leave this company because the work is too easy, I'm not learning anything new, and the pay should be increasing more, considering what I bring to the table. I've tried to bring up these concerns with my boss without sounding like a "flight risk", but it seems that the only way I can demand a suitable raise is with a written employment offer in hand. At that point, it's already too late, IMHO, since it's not a raise, but a counter-offer I'm working with. I never accept counter-offers, since the well is effectively poisoned at that point, and I'll likely be overlooked for future advancement.
I am in late-stage negotiations with a separate company where I have been able to negotiate a whopping 30% increase over my current salary. A few months back, I was able to pull off a 4% raise, but given that local inflation rates are at 2.5% and the cost of housing is exorbitant, only 1.5% of the pay increase was merit based. I do know that my manager went to extraordinary lengths to make a case for increasing my pay substantially, but the idea was shot down by the higher-ups.
Is there some kind of non-generic reason for leaving I could provide my boss with? It seems he's done everything he can to help me, and the company I will be working for has a few employees there that used to work for my current company, so I'm sure gossip will flow. I don't want to say something like "not enough pay", and having that somehow be known to my future employer. Also, I don't want to screw over my old boss with something like "job was too easy".
Is there some way to re-phrase this as something that doesn't make me sound money hungry (gotta pay the bills) or makes my boss look bad?