As far as Im aware a fit note is only advisory, so if an employee feels they are able to attend work the fit note doesn't have to be amended unless your employers liability, or policies, stipulate it needs to be. I've never come across this though.

I just used to cover our backs by documenting a conversation with the employee that they are fit to be in work and making sure they let me or their manager know if they are struggling, and carry out any risk assessments that may be required if its a physical condition.

Seemed pointless to tell them to waste another appointment or a doctors time just to get a note amended when it wasn't needed.

www.nhs.uk/.../

Hi Wendy

I've had the same situation recently, we were happy for the employee to come in but I contacted our insurance company, explained the situation to them and asked if the employee would be covered if they were to return whilst having a fit note stating that they were not fit for work. They advised us that the employee should obtain confirmation from their doctor that they were fit to do and that a a return to work plan should be discussed between him and his doctor and then with us once the doctor see's fit, otherwise he wouldn't be covered.

Hopefully it may be different for you (possibly a different health issue) but it might be worth running it by your insurance provider just to be on the safe side?