What are the wider repercussions of putting in a complaint at work?

[HopeDog]

Just that really. I've complained about the behaviour of a colleague

I put a grievance in about my boss. It was years in the coming and I knew when I did it that it would be the end of my 17 years there. Cost them a lot of money mind 😂
The main lesson I learned is that in the workplace no one is your friend. No heads will go above the parapet. I think so long as you start with that knowledge and get your head around it you will be fine.
I also learned that recordings of conversations can be used in employment issues in certain circumstances. My recordings we're the only things that backed me up and kept me sane when the ranks started to close.
Good luck. It's stressful but I'm so glad I did it.

Thank you. Can I ask why it meant you had to leave your job?

I did this too, also aligned myself with the 'wrong' people. They said they would back me up but didn't. It was the most stressful time of my life. I walked out with no pay. Think very carefully & good luck

I just knew from the bosses character that once I'd made a complaint (highly justified and overdue) he would not react well. I wasn't the only person who had grounds for serious complaint but I was the only one brave enough.
Some people just don't deal well with power, he was one of them.
I was smart in how I went about it, didn't let emotions get in the way. Any communication I had was considered for at least 24-48 hours. He tried to push my buttons and make me react emotionally knowing he would take advantage, but in this case in outsmarted him. HOWEVER! Had it gone pear shaped I imagine the impact it would have had on my mental health would have been dramatic.
The solicitors eventually involved warned me it is one of the most stressful situations to find yourself in, even when you have a good strong case.
Each case is individual and you should consider the big picture with only your own best interests at heart before proceeding. Sometimes it might be better to move on. "Revenge" can be expensive in many ways.

The complaint should be confidential between you, manager, colleague. There should be a meeting when its discussed, you might not be invited to that though and you will both have a chance to put your sides of the situation. If you have genuine concerns then can it be raised as whistleblowing, is it work or competency related? There shouldn't be any repercussions, your manager should deal with it professionally and objectively u less they are false allegations. In reality it can be hard working with someone you complain about, often they don't take it well and become spiteful and like pp said, don't rely on anyone to back you up so dont bother trying to involve anyone else. Main thing is to be professional, don't discuss it with anyone and hold your head high. Involve a union if you have one and dont be a scapegoat if your manager wants the other person out.