Sweden and Finland have agreed to submit applications to join Nato at the same time, perSwedish news

[Ocelot II]

8. If it happens quickly it's because Sweden and Finland already have agreements

with NATO and have been working with the alliance for some time. Otherwise there's still a process:

Sweden, Finland and NATO already work closely together, and according to several Swedish media, this may mean that the formal assessment of the application can go very quickly. Then NATO member states must ratify an addendum to the Atlantic Pact, which forms the basis of the entire alliance.

The Swedish newspaper Dagens Nyheter experiences that the supplement can be presented before the NATO summit in Madrid at the end of June.

Finally, the supplement must be ratified by all 30 member countries. This can take several months, and takes place in different ways in each country. In the United States, the Senate must approve the protocol amendment by a two-thirds majority, while in the United Kingdom, Parliament does not have to hold a formal vote.

Thus, Sweden and Finland can be members of NATO during the autumn.

https://www.aftenposten.no/verden/i/nWxkyQ/sverige-og-finland-skal-vaere-enige-om-mulig-felles-nato-soeknad-i-mai-kan-bli-med-til-hoesten