No obligation at all - you are simply unfit for work. However, you do need to keep submiting your certs when they are due and abide by the provisions of the sick leave policy.
Hi
Just because you are able to go on holidays would not make you fit for work.
There is nothing here: http://www.citizensinformation.ie/c...-and-conditions/leave-and-holidays/sick_leave
that states you should inform your employer if you are going on holidays
Is that any use?
If you are still worried, you could email from the above link for further information to clarify this for you?
Nicola