I have signed an employment agreement with a Swiss Company, with no subsidiary/not presence in Spain. I am a local employee of Switzerland, but I will be working from my home in Spain (tele-working). Do I need to apply for any document in the Social Security in Switzerland to work in Spain.

As far as there is not an international assignment from Switzerland to Spain, Social Security payments will be required in Spain.

To the extent that there is no Spanish Subsidiary/no PE in Spain, the Swiss Company must registered within the Spanish Social Security System to proceed with social tax payments.