Employee Relations
The everyday matters that become expensive if they're handled badly.
By the time an employer asks for help with a performance issue, the pattern is familiar. The problem has been obvious for months. Several managers have mentioned it informally. Nothing is documented. And now something has forced the issue. A customer complaint, a safety incident, or a manager who has finally had enough.
The difficulty is that starting a formal process after a year of apparent acceptance looks, to the employee and often to a tribunal, like something other than performance management.
It's still fixable. It just needs doing properly.

Long enough for genuine improvement to be possible, depending on the role and the issue. Too short looks like a formality; open-ended helps nobody.
No, but you're effectively starting now. Trying to rely on undocumented history is where employers get into trouble. Start properly from this point.
Handle the complaint properly on its own merits. The performance process usually shouldn't simply stop, but how the two run alongside each other matters if the matter is later characterised as adverse action. Get advice before deciding either way.
That changes the process significantly, including obligations around adjustments and how any medical information is handled. Don't proceed on the ordinary performance path without advice.
Tell us what you need and we'll take it from there.
The everyday matters that become expensive if they're handled badly.
Valid reason, fair process, proportionate outcome, and documentation that stands up if the decision is challenged.