CopperEgg bills at midnight central time US on the last day of the month for usage in that month. We bill for your base plan plus any additional hours of monitoring for additional servers or website monitoring packs.

We email statement notices on the first day of the month reflecting payments and usage (pro-rated if your signed up during the month) for the prior month.

Statements are available within your CopperEgg account on the page: Settings Tab > Billing Statements

http://app.copperegg.com#settings/statements