Yes, since the e-vignette is only linked to the number plates of the vehicle, not to the person, you can buy the vignette for another person (e.g. as a gift).
Important: Make sure you enter the correct details of the license plate of the person's car into the system when purchasing the vignette. For errors entering the license plate details no refunds will be issued.
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Is the Swiss e-vignette linked to the car or the person?
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How much does the Swiss Motorway Vignette cost?