I am an Indian citizen and I had visited Poland for a week in April and that Schengen visa (multiple entry) is valid till end of August. I would like to visit Denmark for a month in June. Can I do that ? I have an invitation from the company in Denmark.
Beside the period of validity, there are two other things you have to check to make sure your visa is still valid:
- The number of allowed entries
- The maximum stay (it is to be understood as a grand total across all stays under this visa, except if it is “90” and the visa is valid for more than six months, in which case it means up to 90 days in any 180-day period)
If your new stay would be allowed while respecting all these limitations then you can certainly do it with your current visa.
In particular, having a multiple-entry visa means that you have a lot more flexibility. You are only expected to submit a detailed itinerary and proof of travel insurance for the first journey on the visa and after that it's completely fine to use it for other purposes or destinations.
You should however carry all the documents you would need for a fresh visa application (e.g. itinerary, invitation, travel insurance). You will probably not need them but that would help showing your trip is completely legitimate if any doubt arises at the border.