① Explainer · Licensing concepts
A CPI or RPI indexation clause ties your annual mainframe fee to an external index, and the increase compounds on last year's price. It is one of the quietest escalators in an enterprise contract. Here is the math, a worked five year example, and the caps that bound it.
A single sentence that compounds for years.
An indexation clause ties the annual price increase on a contract to an external index, most often a consumer price index, CPI, or a retail price index, RPI, sometimes with a fixed margin added. Each year the fee rises by the change in that index, regardless of usage. On a multi year mainframe agreement the result is an automatic uplift every single year, set in motion by one clause buried in the price escalation terms. Because the increase applies to the prior year's price, not the original, the effect compounds, and compounding is what makes an unbounded indexation clause one of the most durable cost escalators a buyer signs.
The clause is dangerous precisely because it looks modest. A few percent a year reads as reasonable, so it passes review without challenge, then compounds quietly across a five or seven year term. It also stacks with other escalators: indexation on top of a consumption true up or a renewal uplift produces an effective increase larger than any single clause implies. Reading the escalation terms together is the discipline, and it is central to our contract review service.
How the wording changes the exposure
| Clause form | How it moves | Buyer exposure |
|---|---|---|
| Uncapped CPI | Rises by the full index each year, no ceiling | Highest; exposed to any inflation spike |
| CPI plus a margin | Index plus a fixed percentage, for example CPI plus 2 | High; compounds on an elevated base |
| Lower of CPI or a cap | Rises by the index but never above a fixed ceiling | Bounded; worst case is known |
| Capped with a floor of zero | Between zero and the cap, tracking the index | Bounded both ways; no forced increase in a flat year |
| Fixed annual increase | A known percentage, no index at all | Lowest uncertainty; fully budgetable |
Four percent a year is not twenty over five.
Take an indexed annual fee of 1,000 units rising at a representative 4 percent CPI each year. The increase compounds on the prior year, so after five years the fee is not 1,200 units, the simple sum of five 4 percent steps on the original, but about 1,217 units. The extra is the compounding. Push the rate to 6 percent, or add a CPI plus 2 margin, and the gap widens fast. The illustration below indexes the starting fee at 1,000 units; it is an index, not a price, and it shows the compounding, not a benchmark.
The units are an index and 4 percent is an assumption, not a forecast. The point is the mechanism: compounding turns a modest annual figure into a 21.7 percent rise over five years, and a higher rate or an added margin makes it steeper. A hard cap, for example the lower of CPI or 3 percent, is what bounds the worst case, and replacing indexation with a fixed known increase removes the uncertainty entirely.
The single most valuable change is a ceiling, for example the lower of CPI or a fixed percentage. A cap bounds the worst case regardless of where inflation goes, turning an open ended clause into a known one.
A cap is the difference between a risk and a number.
Name the specific published index and the reference month, and set a floor of zero. Ambiguity favors the vendor, and a floor stops the argument that the clause only ever moves up. Precision here removes future disputes.
An undefined index is the vendor's index.
Where you can, replace indexation with a fixed, known annual increase. A fixed figure is easier to budget and to model than a clause tied to a volatile external number, and it ends the annual uncertainty.
A known increase beats a clever one.
Indexation stacks with consumption true ups and renewal uplifts. Model them together to see the real trajectory, because the effective annual increase is larger than any single clause read in isolation suggests.
Escalators compound on each other, not just on the price.
A term tying the annual price increase to an external index, usually CPI or RPI, sometimes plus a margin. The fee rises each year regardless of usage, and because the increase compounds on the prior year, an unbounded clause is a durable cost escalator.
More than the headline, because it compounds. A 4 percent clause adds about 22 percent over five years, not 20, and index plus a margin compounds on a higher base. The annual figure looks modest; the cumulative term effect is where it bites.
A hard annual cap such as the lower of CPI or a fixed percentage, a named index and reference month, and a floor of zero. Where possible replace indexation with a fixed, known increase that is easier to budget and model.
In price escalation, annual fee adjustment, and maintenance increase sections, and in renewal terms referencing an index for out year pricing. They stack with true ups and renewal uplifts, so read the escalation terms together.
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