公共工事に物価変動調整式を適用する

Record against the contract each component the clause names and its weightage, which index series applies to each, what the base date is, whether a minimum period must pass before anything is payable, and whether a ceiling applies.

理由: The clause is read once, at the start, by whoever is available, and then applied for years by other people. Turning it into stated parameters at that first reading is what stops the third claim being computed on a different understanding from the first.

Bring in the published series for each component, record the base month value the contract fixes, and add each period's value as it is published. Where a series is revised after publication, keep both the provisional and the final figure.

理由: Index series get revised, and a claim computed on a provisional figure has to be reworked when the final one lands. Holding both makes that a recomputation rather than a discovery, and it explains the difference to the checker before they ask.

Take the value of work executed in the period from the bill, split it by the weightages, apply each component's index movement, and keep the working visible per component rather than as a single figure.

理由: Escalation is checked by re-doing it, not by reading it. Working that shows the split, the two index values and the resulting amount for each component can be verified in minutes; a single total invites the checker to compute their own and argue about the difference.

Put the adjustment on the running account bill as a separate line naming the period and the clause, and let the tax and the deductions treat it the way the contract and the invoice rules require.

理由: Escalation folded into rates makes the rates untraceable to the contract and the escalation untraceable to a period, so both become unverifiable at once. Kept as a line, it can be certified, queried or withheld on its own without touching the measured work.

File the published index pages used, the value of work certified for the period, and the working, all keyed to the period, so any single month can be produced on its own.

理由: Escalation is settled at the end of the job as often as during it, by which time the person who computed period four has left. A file organised by period answers a query about period four; a file organised by year does not.