Registration for most courses within the Chemistry master's programme is done via the UvA, even if the courses themselves take place at the VU.
A small number of courses are part of other programmes which are taught only at the VU. Course registration for these select courses takes place via the VU registration system. Details can be found in the document below.
To be able to access the VU systems, a VUNetID is required. All students of the Master Chemistry (joint degree) programme recieve both an UvANetID and VUNetID. Please note though that you need to fully finish your master's admission process (having shown your bachelor's diploma and paid tuition) before both your VUNetID and UvANetID are activated. Up till then, only the NetID of the university where you originally registered is active.