Billed vs. amortized cost
Cost Explorer can show two different numbers for the same spend: billed and amortized. A toggle above the chart switches between them.
Billed cost
Section titled “Billed cost”Billed cost is what the provider charged in that billing period. If you pay for a 1-year AWS Reserved Instance upfront, the full amount lands as one charge in the month you paid it — followed by months of near-zero cost for the compute it actually covers.
Amortized cost
Section titled “Amortized cost”Amortized cost spreads a prepaid commitment across the term it covers, instead of showing it as a spike on the day it was paid. This applies to prepaid or committed-spend products: AWS Reserved Instances and Savings Plans, and Azure reservations. FOCUS-formatted billing data carries its own effective cost field. GCP doesn’t report an amortized figure.
Example: you buy a 1-year AWS Reserved Instance for $1,200, paid upfront in January.
- Billed view: January shows a $1,200 spike. February through December show close to $0 for that instance.
- Amortized view: January through December each show $100 — the $1,200 divided evenly across the 12 months the RI covers.
The amortized view is closer to what the compute actually cost you each month. The billed view is closer to what hit your card.
Which providers report a real amortized figure
Section titled “Which providers report a real amortized figure”Only three sources currently publish their own distinct amortized number:
- AWS — Cost Explorer’s amortized cost metric.
- FOCUS-formatted billing data — the effective cost field.
- Azure — Cost Management’s amortized cost query.
Every other source writes the same value for amortized as for billed. This isn’t a fallback or a limitation — for a SaaS subscription or an LLM API bill, there’s no prepaid commitment to spread, so the charge you’re billed is the cost for that period. Billed and amortized are the same number by definition, not because Plutus couldn’t compute something better.
Amortized data has a start date
Section titled “Amortized data has a start date”Amortized figures are only captured starting 2026-08-04. For accounts connected before that date, earlier cost data shows the billed figure in the amortized view too, because the amortized number was never requested from the providers at the time it was ingested — and none of them can retroactively supply it. AWS Cost Explorer’s own lookback window, for example, isn’t long enough to reconstruct arbitrary history.
Cost Explorer flags this on screen. The note is based on your account’s own data: it uses the earliest date where your amortized cost differs from your billed cost. When the amortized view covers dates before that, the chart shows a note that earlier periods are the billed figure, not a genuine amortized figure. An account with no commitments has no such date, so it never shows the note.
Budgets and alerts always use billed cost
Section titled “Budgets and alerts always use billed cost”If you’re viewing amortized cost and a budget alert fires, the dollar amount in the alert can differ from the amortized number on screen. This is deliberate: enforcement needs a figure that can’t shift depending on how a commitment is being spread, the same reason budget and spend-limit math is pinned to a fixed currency rather than floating with exchange rates (see Multi-currency support). If you have significant Reserved Instance or Savings Plan coverage, expect the number that triggers an alert to sometimes read higher than what the amortized chart shows for the same day.