Your employer should have given you information about their grievance procedures, which you should try to follow. This would normally be in the Company Handbook, a manual, your contrract, or an online portal. If there isn't a formal procedure, you can follow Acas guidance, which sets out the standards of fairness and reasonable behaviour that both sides should follow when there is a dispute.
The information below is the most normal route that you would be expected to follow.
Talk to your manager
You should try to sort the problem out informally first before you take any formal action, so the first step is to talk to your manager. If you don't feel able to talk to your manager, you could instead speak to someone else who is in a position of authority.
If this doesn't solve the problem, or if you feel it's not possible to deal with this informally, you can start an official grievance. This would normally begin with a letter that details the problem along with any resolutions you would like. Make sure you keep a copy of everything you write. Citizens Advice has a template letter you can use, along with a checklist.
Your employer should then arrange a meeting to discuss your grievance. You have a right to bring a colleague or a trade union representative to the meeting and you should be given the opportunity to explain your case. After the meeting, your employer should write to you with the decision.
Appealing a grievance decision
If you don't agree with the grievance decision, you can write a letter of appeal explaining why you disagree.
You should be invited to another meeting to discuss the appeal, and (if possible) it should be handled by someone more senior than your manager. Again, you have a right to bring a colleague or a trade union representative to the meeting and you should be given the opportunity to explain your case. After the meeting, your employer should write to you with the decision.
Taking it further
If you're still not satisfied, you have the option to try mediation or other forms of dispute resolution. You could also potentially take your case to an employment tribunal (see below).
If you would like to try mediation, both you and your employer would need to agree to it. Mediation is where an independent, impartial person helps both sides come to a solution that is acceptable to everyone; the mediator may be from your organisation or your employer may pay for an external mediator.
Acas offers a dispute resolution service that you can read about on their website, and you must always contact them before you can take a case to the employment tribunal so they can offer you free Early Conciliation.
You don't have to go through a grievance process before making a claim to an employment tribunal but there is a risk you it would impact your case and could reduce any compensation award. We would therefore advise trying to resolve your problems through your employer's processes before taking your case to a tribunal.
However, it is important to remember the deadline to make a tribunal claim is three months minus one day from the date that your issue last happened. This is the deadline even if you've been going through the grievance process, but it can be extended if you tell them you're going through Early Conciliation with Acas.
Employment tribunals are free but you may want to pay for legal advice.
You can read more about making a claim to an employment tribunal on the Acas website and on the Government website.