[Chris W]

There is no requirement for written notice of an investigation.

An investigation is simply a meeting to assertain facts. The employer and employee are both entitled to have witnesses present if they chose.

What the parties say in the meeting is recorded and both parties then sign to agree that what is written is a true record of what was said. Both the company witness and employee witness do not speak during the witness and are merely present for verification [although commonly the company witness will be the person recording the meeting].

The information obtained in the investigation and any other evidence will then be evaluated and then disciplinary proceedings may or may not go ahead. If a disciplinary hearing does take place written notice (at least 7 days iirc) is required. The employee is required to attend, and if he/she doesn't a second meeting will be scheduled. If again he/she doesn't attend a third meeting will be scheduled but in the event of the employees no attendance the hearing will be held in his/ her absence.

That said, the investigation in itself is nothing to worry about.