First of all, being placed on suspension is not an automatic assumption of guilt and does not amount to disciplinary action. Whilst it can lead to disciplinary action, it is primarily there to be used as a precautionary measure whilst an employer investigates any serious allegations against the employee. Reasons for suspending could be in the case of gross misconduct, breakdown of relationship, risk to an employer's property, their clients or other employees, to preserve evidence or ensure it is not tampered with, avoid potential witnesses being pressured or intimidated, etc.
Ideally the suspension should be followed up with a letter confirming the suspension and outlining the reasons for it, although this is not a legal requirement, just good practice.
The period of suspension should be as short as possible and kept under regular review. During that period the employer should conduct a reasonable investigation into the allegations against the employee. If the investigation gathers enough evidence to justify taking disciplinary action, the employee has the right to be informed in advance of the allegations and evidence to be used against them and be given the opportunity to prepare to defend themselves at the forthcoming hearing.
On the other hand, if the investigation does not find enough evidence to justify a disciplinary, the employer should terminate the suspension immediately and allow the employee to return to work as normal.
In terms of the investigation, if you are signed off sick, the employer should place the investigation on hold until you are fit to attend and participate. They could eventually ask you to participate remotely such as answering questions over the phone or in writing but they should not jump to that unless there has been a long delay due to you being off and there is a time critical need to proceed with the investigation.
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