Downgrade to Level 0 at the start of the billing period

My billing period ends at April 9 and I would like to downgrade to Forms Level 0 immediately when it ends. When it ends, will I still have to pay for the first day of the new billing period? I’m asking because I want to remove the credit card info right after downgrading from Level 1 and I don’t want to have my site taken down just because I haven’t paid for 1 day.