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Adjustment of the contract price (GB/T 50500-2024 Chapter 8): eleven triggering events, mechanism by section, and FIDIC mapping

Adjustment of the contract price is the mechanism for changing the contract price during performance. GB/T 50500-2024 Cl. 8.1.1 lists eleven triggering events: BOQ errors, provisional sums, PC sums (provisional estimates), contractor's services, dayworks, changes in costs, changes in laws and policies, variations, additional works, claims, and other events agreed by the parties; the procedure runs submit, check, re-check, review and confirm (8.1.2). Key mechanics: BOQ errors and variations share one re-rating ladder (identical items at contract rates; analogous items converted; different items negotiated), with a 15% quantity boundary for re-rating (8.2/8.9); provisional sums are controlled by the employer and any unused balance reverts at final account (8.3); PC-sum items are replaced by tender prices — materials pre-VAT, specialist works VAT-inclusive (8.4); dayworks are measured under 7.5 (certified dayworks records) and priced at the BOQ daywork rates (8.6, with deemed approval if verification is overdue, 7.5.5); changes in costs are adjusted beyond the agreed band — 5% by default — by index-based (formula) adjustment or adjustment based on published price information (8.7 + Annex A), the differential carrying VAT only; changes in laws pivot on the base date, adjusting price and/or time for enactments, amendments, repeals or new interpretations after it, with no upward adjustment during contractor-caused delay (8.8); additional works may follow contract rates or freshly negotiated rules under a supplementary agreement (8.10); claims cover events outside 8.2-8.10 — compensatory, not punitive, and mutual, with profit added for eight categories of employer-risk events (8.11). FIDIC counterparts sit scattered across Clause 13 (variation valuation 13.3, provisional sums 13.4, changes in laws 13.6, changes in cost 13.7 — 2017 numbering) and Clause 20 claims (28-day hard time bar): adjacent institutions, not chapter-for-chapter equivalents.

Applicable Codes

  • GB/T 50500-2024 建设工程工程量清单计价标准（第8.1.1/8.1.2条、第8.2～8.11节、第7.5节、App. A、App. G）
  • FIDIC Red/Yellow Book 2017（第13.3、13.4、13.6、13.7、20.2.1 条〔对照〕）
  • GB/T 50875-2013 工程造价术语标准

Adjustment of the contract price answers when, how and through what procedure the contract price changes during performance. GB/T 50500-2024 Chapter 8 breaks it into eleven triggering events. Practitioners most often look up: the list of triggering events (8.1.1); the ±15% quantity boundary and the re-rating ladder for variations; the band and methods for cost adjustment (8.7 + Annex A); the adjustment rules for PC sums and provisional sums; and the boundary against claims. This card walks the mechanism section by section (8.1-8.11), maps it onto FIDIC Clauses 13 and 20, and navigates the related cards in this domain.

Concept and mechanism

Events and procedure (8.1). On the occurrence of any of the eleven events in 8.1.1 (BOQ errors; provisional sums; PC sums; contractor's services; dayworks; changes in costs; changes in laws and policies; variations; additional works; claims; other agreed events), the parties adjust the contract price under Chapter 7 and this chapter. The contractor computes quantities under Chapter 7, prices the adjustment under 8.2-8.11 and submits it with supporting documents within the agreed time; the procedure is submit, check, re-check, review, confirm (8.1.2).

BOQ errors and deviation (8.2). Under a re-measurable (unit-rate) contract, the billed items are re-measured against contract drawings; missing or erroneous items, mismatched item descriptions and quantity deviations are BOQ errors. Deviations up to 15% (inclusive) follow the variation re-rating ladder (8.9.1); beyond 15%, rates are reasonably adjusted down for increases and up for decreases (8.9.2), reflecting purchasing-price economies of scale. Preliminaries generally do not adjust for BOQ errors (statutory HSE items excepted). Lump-sum contracts are barred from adjusting for BOQ quantities falling short of drawings.

The three 'other amounts' (8.3-8.5). Provisional sums are held and used by the employer on instruction; unused balances revert to the employer at final account; work financed from them is measured and priced as a variation, VAT included. Where PC-sum materials or specialist works must be tendered by law, the accepted tender price replaces the estimate — materials at pre-VAT prices, specialist works VAT-inclusive (8.4). A switch between employer-supplied (free-issue) materials and contractor-supplied materials adjusts the all-in unit rate and the contractor's services charge together (8.5).

Dayworks (8.6). Work not suitably priced off the BOQ may be priced as dayworks: measured under 7.5 (dayworks records submitted and certified by both parties; 7.5.5 keeps deemed approval if verification is overdue) and multiplied by the BOQ daywork all-in rates; certified quantities exclude the contractor's own management staff and plant already on site.

Changes in costs (8.7 + Annex A). The adjustable heads are limited to labour, materials, and fuel/power within plant and machinery charges; against the base-date price from the agreed published-price source, movements beyond the agreed band — 5% by default — are adjusted by index-based (formula) adjustment or adjustment based on published price information (Annex A.2); the adjustable material list may be locked by the Annex G schedule; the differential carries VAT only, with no overheads or profit, and 8.7.6 lists eight cost heads that do not adjust.

Changes in laws and policies (8.8). The base date is the pivot: enactments, amendments, repeals or changed interpretations after it that move cost and/or time are adjusted per the contract and cost-authority rules; where the contractor caused the delay, upward movements do not adjust during it and downward ones do; abnormal market movements hitting work pushed past the planned dates adjust under the cost rules.

Variations (8.9). The re-rating ladder: identical conditions and item descriptions — contract rate; analogous — converted from contract rates; different — negotiated by reference to analogous rates and bid levels; omissions that materially change site conditions — negotiated on actual conditions and market prices. BOQ errors (8.2) share this ladder and the 15% boundary.

Additional works (8.10). Works outside the contractual scope done at the employer's request: priced off the measurement standards plus contract rates and bid levels, or under freshly negotiated measurement and pricing rules in a supplementary agreement or separate contract; the contractor submits its method statement, programme and priced BOQ for review before execution.

Claims (8.11). Events caused by the other party, outside 8.2-8.10, causing loss and/or delay, are pursued as claims — compensatory, not punitive, and running both directions; cost and time claims are made together, and amounts already adjusted under the price-adjustment rules are not claimed twice. Eight categories of employer-risk events additionally carry profit. The 28-day notice wording moved from the 2013 'right forfeited' to the 2024 'may be deemed' formulation.

International mapping (FIDIC)

Chinese term/mechanism FIDIC term Relation Point
Adjustment of the contract price (Ch.8, eleven events) Clause 13 [Variations and Adjustments] + 14.1 (Contract Price subject to adjustments) adjacent China lists events in one chapter; FIDIC scatters them across variation, provisional sums, law/cost adjustment and Clause 20 claims
Variation (8.9) variation (Clause 13) adjacent FIDIC: Engineer-instructed, one route regardless of origin; China: multi-party certification chain
Additional works (8.10) variation / additional works adjacent FIDIC values in-contract and extra work alike as variations; China runs a separate channel that allows re-negotiated rates
Variation valuation (8.9.1 ladder) valuation of variations (13.3.1) adjacent Both start from contract rates; FIDIC allows provisional rates in interim payments
BOQ errors (8.2) re-measurement (measurement of the works) adjacent FIDIC absorbs quantity risk by re-measurement; China adds the ±15% re-rating boundary and lump-sum bars
Provisional sums (8.3) provisional sums (13.4) equivalent Employer-controlled in both; unused balance never accrues to the contractor
PC sums (8.4) provisional sum for specified materials / nominated works adjacent China substitutes accepted tender prices; FIDIC works through nomination and PC sums
Dayworks (8.6) dayworks adjacent Same term; China requires certified dayworks records before pricing
Cost adjustment (8.7/Annex A) adjustments for changes in cost (13.7, 2017 no.) adjacent China: default 5% band, two methods; FIDIC: applies only if cost-indexation schedules are included
Changes in laws (8.8) adjustments for changes in laws (13.6, 2017 no.) adjacent Both pivot on the Base Date / contract base date
Claims (8.11) claims (Clause 20; Notice of Claim 20.2.1) adjacent China: 28 days, 'deemed' wording; FIDIC: 28 days, hard time bar

Key difference: FIDIC concentrates adjustment power in the Engineer's agreement or determination; China rests it on documents certified by both parties. FIDIC has no consolidated list of adjustment events — map item by item. Usage warning: write 'adjustment of the contract price', not 'contract price change'; and do not go looking for a Chinese-style eleven-event checklist inside a FIDIC book.

Card-group navigation

Related cards in this domain, grouped by sub-topic (covering each adjustment mechanism and the frequent dispute scenarios):

General framework and risk (4)

BOQ errors and quantity deviation (4)

Variations (4)

The site-instruction channel and dayworks (1)

PC sums and provisional sums (4)

Cost adjustment: general (10)

Cost adjustment: published price information (9)

Cost adjustment: materials and scenarios (9)

Sector adjustment (railway) (2)

Contract forms and adjustment channels (4)

Settlement-side adjustments (5)

FIDIC comparison (1)

Keywords

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