You can travel with the Arlanda express using your special transport services card from the Stockholm County Civil. You do not need to buy a ticket in advance, just show your card to the train conductor. Then you pay for the journey afterwards via an invoice, along with your other special transport services.
For info on assistance with Special transport services and more, please visit [Färdtjänstens website](https://fardtjansten.regionstockholm.se/ "färdtjänsten") (Swedish only) or call +46 8 720 80 80.