Research / Tools
Mid-term amendment & rollover simulator
Run a usage contract through an upgrade or downgrade. See how rolled-over credits carry across, what the wording of the rollover cap is worth, and what rerunning the contract from month one would do to invoices you've already sent. Then copy a worked example for the order form.
Everything is calculated in your browser. The numbers you enter aren't sent anywhere.
Month by month
Every unit in the order it was drawn: rolled-over units first, earliest expiry first, then the month's included units, then overage.
Lapsed: included units above the rollover cap, rolled-over units that expired, and anything that lapsed on the amendment date.
Rollover lots, each with its own expiry
Write the rule into the order form
A worked example in the contract means finance and the customer read the same numbers. This wording updates as you change the terms above.
Illustrative wording generated from the terms above. It isn't legal advice: have your counsel adapt it to your agreement before you use it.
Where the clause is silent, the defaults in our notes on amendments and on rollover caps explain the choices.
Run this on your real contracts
Send 3–5 redacted contracts, amendments included, and the usage behind them. We model each amendment as its own segment and recalculate every true-up against what was invoiced, with each line traced to its contract clause.
Get a free leakage auditFree, within 48 hours of complete files. Redacted files only, deleted 30 days after delivery. How we handle audit files.
Tiered overage or free allowances?
This simulator uses one overage rate for each set of terms. For overage tiers that accumulate or reset monthly, free monthly units and grace allowances, use the true-up calculator.
Open the true-up calculatorHow the simulator handles an amendment
- The original terms stop on the effective date. Months before it are never recalculated.
- A mid-month date splits the month. Each part gets included units prorated by days, rounded to whole units, and its own overage rate. Usage is split by days unless you enter the part before the change.
- Unused credits carry across, or lapse. If they carry, rolled-over units keep their original expiry, and included units left in the first part of the month can be used until the month ends.
- The amended terms apply from the effective date, including the new rollover cap.
Rollover, one lot at a time
Each month's rollover is a separate lot with its own expiry. Usage draws on the earliest-expiring lot first, then the month's included units, then overage. Rolled-over units don't roll again. In the two parts of a split month, the cap applies to that part's prorated included units.
What it leaves out
Overage tiers, free allowances, minimum-commit shortfall charges, several metrics on one contract, renewals, and usage that arrives after a month is invoiced. Rollover still open when the term ends lapses.
Questions every amendment should settle
What happens to rolled-over credits when a contract is amended mid-term?
They usually carry into the amended terms and keep their original expiry dates; a plan change doesn't give them a new clock. Some contracts forfeit them on the effective date instead. Either works, as long as the amendment says which.
Is a rollover cap a percentage of the commitment or of the unused balance?
It depends on the wording, and the same sentence is often read both ways. On a 10,000-unit month with 4,000 unused, a 20% cap carries 2,000 units forward if it applies to the commitment and 800 if it applies to the unused balance. The difference shows up as overage the next month. Read the field notes.
Should the contract be recalculated from the start?
No. Months before the amendment were billed under the terms in force at the time. Rerunning them on the new terms turns correct invoices into credits. Start the new terms on the effective date, and post any correction to an earlier month as an adjustment on the next invoice. Why the ledger should be append-only.
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