Which period's published price applies to settlement material prices: the two-date system — base price locked at the contract base date (28 days before bid closing) plus period-by-period pricing per measurement cycle (GB/T 50500-2024 Annex A.2 price-information method)

Topic Positioning

Answers "which period's published price applies to material price adjustment at settlement (incl. process and completion settlement)": not one period, but "base locked at the contract base date + period-by-period current prices per measurement cycle", each cycle's adjustment computed and totaled into the completion settlement. Per GB/T 50500-2024 (price-information method, Annex A.2) and related clauses.

Core Conclusions

1. First principle: contract governs. Unit-price contracts should agree the adjustment method beyond the risk range — "express agreements are followed; absent or unclear, adjust by national, local, or industry rules/standards" (T/ZBD 100.5-2023, 3.1.7). The parties shall fix the adjustable main materials via Annex G.2 Tables G.2.1-1/-2 as contract annexes; materials outside the list do not adjust (3.3.5).

2. Base price C0 — locked at the contract base date, not drifting with construction. The base date is 28 days before bid closing (non-tendered: 28 days before signing), the reference date for price adjustment (2.0.21). C0 sources: (1) market prices used by the employer for the bid ceiling; (2) the cost authority's seasonal/monthly published price at that date; (3) same-condition trading-center award prices of similar projects within the prior month — all representing the level 28 days before closing; the tenderer shall state the source, publisher, and season/month in the tender documents (A.2.1).

3. Current price Ci — per measurement cycle. Ci is the "cycle market price": (1) jointly confirmed market price of that cycle; (2) the cost authority's seasonal/monthly published price; (3) same-condition trading-center award prices within the prior month — representing the cycle's current level (A.2.1). The adjustment △P is defined "per measurement cycle" — not a single terminal period.

4. Adjust only beyond the band, only the excess. Contractual bands first; absent or unclear, when labor, materials, or fuel/power within machinery fluctuate beyond 5%, adjust per an Annex A method; within band, no adjustment (8.7.2). With base = 28-days-before-closing published price and current = cycle published price, adjust symmetrically in three cases by the bid-vs-base relation (A.2.4): (1) bid < base — rises measured from base, falls measured from bid, excess adjusted; (2) bid > base — falls from base, rises from bid; (3) bid = base — both from base.

5. Special cases:

• Provisional adjustment (A.2.2): without cycle market info or under major dispute, provisionally use the authority's published price and true up later per actual market info.
• Multiple prices within a cycle (A.2.3): use the arithmetic mean, a quantity-weighted mean of price vs completed quantity, or the price over the main-consumption period; the parties shall agree the method and precedence.
• Delay (8.7.4): employer-caused extension — subsequent works priced at the higher of planned vs actual progress dates; contractor-caused — the lower; otherwise per 8.7.2 (subject to contract/law).

6. Settlement total. Cycle adjustments accumulate; "price-change adjustment" is item 7 of the completion settlement (10.3.2). Signed process-settlement files form part of the completion settlement without re-measurement or re-pricing (10.2.3); exception — measure fees and prime-contractor service fees are provisional in process settlement and are recomputed at completion (10.2.7).

7. VAT. Adjustments to labor, materials, and fuel/power within unit rates carry VAT but not management fee or profit (3.3.5).

Applicable Boundaries

• Applies to BOQ projects under GB/T 50500-2024 adjusting by the price-information method (A.2) at process and completion settlement; express contractual methods (e.g., index method A.1), sources, and periods govern.
• Lump-sum contracts: absent agreement, no adjustment for fluctuation; claims of changed circumstances or extension go through claims (T/ZBD 100.5-2023, 3.1.7).
• Construction machinery rates: generally unadjusted absent express agreement; only fuel/power of major plant may follow the material method.
• Only listed labor/materials/plant adjust; adjustments carry price change and tax only.

Further Reading

• GB/T 50500-2024: 2.0.21, 3.3.5, 8.7.1-8.7.4, 10.2.3/10.2.7, 10.3.2, Annexes A.2.1-A.2.4, G.2.
• T/ZBD 100.5-2023, 3.1.7.
• Comparison: index method in GB/T 50500-2024 Annex A.1.