Monthly budgets are divided into a daily spend total, and ads run on a schedule until they hit their daily spend cap.

Example: On a 7 day/week ad schedule, a monthly budget is divided by the average number of days in a month (30.4 days) to calculate the daily ad spend. A $2,000/mo ad spend budget would therefore have a daily budget of $65.79/day.

Most Google Ads accounts use automatic payments as a means of paying for ads, wherein you first accrue advertising costs, then have those costs charged to a credit card afterward.

Credit cards are charged for their past advertising spend on the first day of every month and whenever an account reaches a predetermined payment threshold set by Google.

Example: Suppose Google sets a standard payment threshold of $750 based on spend, account history, country, and currency. This account will be charged automatically on the 1st of each month for whatever balance exists at that time. Additionally, if this account's balance reaches its $750 ad spend payment threshold before that date mid-month, it will be immediately charged as well. On a $2,000/mo budget and daily spend of $65.79/day, this account would be charged on the first of each calendar month and then approximately every 11 days.

How quickly an account reaches its threshold can vary depending on a wide range of factors, and some accounts may reach their threshold several times per month. Over time, Google may choose to increase an account's payment threshold to reduce billing frequency, meaning fewer transactions but for higher amounts.