Looking at Migrationsverket's article about entering Sweden without a visa, it states that if you don't fulfil the 450 SEK per day requirement, you can alternatively provide a "a written invitation from your family member or friend that you will be staying with"1. What's not clear from the article is what a "written invitation" actually entails. As such, I would like to know, what exactly is required from this written invitation? Is a text message on a messaging service enough, or does it need to be a printed formal letter? What should the contents of the text be?
The form and instructions on how to use it are available here: https://www.migrationsverket.se/download/18.5e83388f141c129ba631285c/1666876596848/241011_Inbjudan_en.pdf
The invitation form covers eg the personal details of the individual issuing the invitation and their relationship with the applicant, the proposed itinerary and financial details of the visit, and the applicant’s details.
Non-visa nationals who don’t fulfil the 450SEK per day requirement and need to be able to demonstrate adequate subsistence at the border if asked, may carry the invitation form or an equivalent (eg a letter covering the same topics as the form) with them.
The person issuing the invitation must send the completed form together with the required attachments by mail or scan them and send them via email to their relative or friend abroad.
Visa nationals must submit the form with its attachments together with their application for Schengen visa.