Understanding your reservation line items
RIs provide you a significant discount compared to On-Demand Instance pricing. RIs aren't physical instances. They're a billing discount applied to the use of On-Demand Instances in your account. These On-Demand Instances must match certain attributes to benefit from the billing discount.
In the following tables, the columns and rows from AWS CUR are transposed for clarity. The values in the first column represent the headers of a report. These examples include only a few key AWS CUR columns. To learn more about other AWS CUR columns, see the Data dictionary.
Upfront fee
The Fee line item is added to your bill when you purchase
an All Upfront or Partial Upfront RI.
The following table shows how this one-time fee appears in some AWS CUR columns.
| lineItem/LineItemType | Fee |
| lineItem/ProductCode | AmazonEC2 |
| lineItem/UsageStartDate | 2016-01-01T00:00:00Z |
| lineItem/description | Sign up charge for subscription: 363836886, planId: 1026576 |
| lineItem/UnblendedCost | 68 |
| Reservation/ReservationARN | arn:aws:ec2:us-east-1:572481847476:reserved-instances/f8c204c1-dd48-43f1-adb8-f88aa61e0dea |
Recurring monthly RI fee
The RI Fee line item describes the recurring monthly charges that are associated RIs applied that month. The RI Fee initially is added to your bill on the day of purchase and on the first day of each billing period thereafter.
The RI Fee is calculated by multiplying your discounted hourly rate and the number of hours in the month.
The following table shows how the recurring monthly charges appear in the report.
| lineItem/LineItemType | RI fee |
| lineItem/ProductCode | AmazonEC2 |
| lineItem/UsageStartDate | 2016-01-01T00:00:00Z |
| lineItem/UsageType | HeavyUsage: m4.large |
| lineItem/description | USD 0.0309 hourly fee per Linux/UNIX (Amazon VPC), m4.large instance |
| lineItem/ normalization factor | 4 |
| lineItem/UnblendedCost | 23 |
| Reservation/AvailabilityZone | |
| Reservation/ReservationARN | arn:aws:ec2:us-east-1:572481847476:reserved-instances/f8c204c1-dd48-43f1-adb8-f88aa61e0dea |
| Reservation/TotalReservedunits | 744 |
| Reservation/TotalReservedNormalizedUnits | 2976 |
Recurring monthly charges are recorded differently for RIs that have an Availability Zone or AWS Region Region scope. For RIs that have an Availability Zone scope, the corresponding Availability Zone is shown in the reservation/AvailabilityZone column. For RIs that have a Region scope, the reservation/AvailabilityZone column is empty. RIs with a Region scope have values for the lineitem/NormalizationFactor and reservation/TotalReservedNormalizedUnits columns that show the instance size.
RI discount benefits
The Discounted Usage line item describes the instance usage that received a matching RI discount benefit, and is added to your bill when you have usage that matches one of your RIs. AWS calculates RI discount benefits based on matching usage: for example, the use of an instance that matches the instance reservation. If you have matching usage, the cost associated with the usage line item is always zero because the charges associated with RIs are already accounted for in the two other line items (the upfront fee and the recurring monthly charges).
The following table shows an example of usage that received an RI discount benefit.
| lineItem/LineItemType | DiscountedUsage |
| lineItem/ProductCode | AmazonEC2 |
| lineItem/UsageStartDate | 2016-01-01T00:00:00Z |
| lineItem/UsageType | BoxUsage:m4.large |
| lineItem/description | Linux/UNIX (Amazon VPC), m4.large Reserved Instance applied |
| lineItem/ResourceID | i-1bd250bc |
| lineItem/AvailabilityZone | us-east-1b |
| lineItem/normalizationfactor | 4 |
| lineItem/NormalizedUsageAmount | 4 |
| lineItem/UnblendedRate | 0 |
| lineItem/UnblendedCost | 0 |
| Reservation/ReservationARN | arn:aws:ec2:us-east-1:572481847476:reserved-instances/f8c204c1-dd48-43f1-adb8-f88aa61e0dea |
The value for UsageAmount in the Amazon EC2 DiscountedUsage line is the actual number of hours used. The value for NormalizedUsageAmount is the value for UsageAmount multiplied by the value for NormalizationFactor. The value for NormalizationFactor is determined by the instance size. When an RI benefit discount is applied to a matching line item of usage, the Amazon Resource Name (ARN) value in the reservation/ReservationARN column for the initial upfront fees and recurring monthly charges matches the ARN value in the discounted usage line items.
For more information about mapping instance size to normalization factor, see Support for modifying instance sizes in the Amazon EC2 User Guide for Linux Instances.
