It is not compulsory to use a formal workplace procedure before bringing a claim to a tribunal. In fact, given the tight timetable in which to lodge a tribunal claim (just three months) this may not always be possible.
However, if your failure to follow a workplace procedure amounts to an unreasonable breach of the Acas Code of Practice on Disciplinary and Grievance Procedures (PDF, 167KB), this can result, in some circumstances, in a cut to your compensation by up to 25%. However, this works both ways – if your employer unreasonably breaches the procedure, the tribunal can decide to increase your compensation by up to 25%.
In addition, Acas would normally expect you to have tried to resolve your dispute using your employer’s grievance procedure before attempting Acas early conciliation – but not if this means that you risk missing the deadline for your employment tribunal claim.