Settings, then Delete account. It happens at once, and it cannot be undone.
Your upcoming events are cancelled when you confirm, and the people who said yes or not sure are told. Every scheduled message stops, and your events, your address book and your invites go with the account.
Thirty days later the guest records that were yours are anonymized, so what remains cannot be traced back to a person.
Two things are kept longer. The contents of messages are kept 180 days, because we must be able to show what was sent and on what basis, then purged. Opt-out records — a phone number and the fact that it said stop — are kept for as long as we run, because throwing one away would mean texting someone who told us not to.
If you want a copy of anything, or a refund, ask at help@simpleinvite.app before you delete. Afterwards there is nothing left for us to send you.