Second entry with Schengen visa - staying at my boyfriend with no formal invitation

[CloudyNow]

I obtained a multi-entry Schengen visa from Germany which I used for the stated purpose. Now I'm travelling to Luxembourg and this time I am staying over at my boyfriend. He is a resident there but we didn't bother writing a formal invitation letter since I already had a visa. Will the border police refuse to let me in if I don't have a formal invitation? I do have a return flight booked.

[Caravel88]

They reserve the right to ask you the same documents you provided to get the visa, which includes financial evidence, proof of where you will be staying, etc. As long as you provide satisfactory answers it is unlikely you will be refused entry. There is a chance they might not ask for anything either.

I obtained a multi-entry Schengen visa from Germany which I used for the stated purpose. Now I'm travelling to Luxembourg and this time I am staying over at my boyfriend. He is a resident there but we didn't bother writing a formal invitation letter since I already had a visa. Will the border police refuse to let me in if I don't have a formal invitation? I do have a return flight booked.