You can set cost alerts for Azure in order to be alerted if the spending is going out of control. This is an easy way to make sure your budgets are within the limit and not exceeded.
First, go to resource groups and select the resource group you need to set the alerts.
Then select 'Budgets' in the options pane as shown below.
Then select the following fields accordingly.
Scope: You can go to 'Change Scope' and select a different resource group or even select the subscription itself as whole.
In the Budget Details section set Name, Billing Period, Start Date (disabled for month options), expiration date. Billing period can be set in measures of units in invoice or calendar based. This means if your bill is calculated on 15th, Invoice option will take 15th to 15th. If you select Calendar, it will calculate 1st day of the month to end of the month.
Then under Budget Amount, select the Amount.
Click 'Next' button to go to the alerts section.
In the 'Set Alerts' window set the budget percentages and Action Group. If you do not have any action groups, then you can add individual recipient emails. Click 'Create' button to create the alert.
Once created, it will show up in the Budget section of the resource group.