面對「因工期展延導致間接成本支出的增加」，若遲延原因可完全歸責於業主，則承包商可提出索賠，實務上計算索賠常用的方法是「比例法」與「實支法」，這兩種方法雖都有其優點，但於間接成本的計算上，其結果卻都不符合實際情況，例如比例法計算迅速但不精確；而實支法精確但過於繁雜，且證明困難。 目前國外有一種源於製造業的「作業基礎成本法（Activity Based Costing, ABC）」，因特別強調作業消耗資源的真實情形（包括直接與間接成本），故可提供管理者準確分析後的產品真實成本；本研究即欲以ABC之精神與觀點，分析「因展延所生間接成本」的索賠，找出較符合實際情況的計算方法。 若承包商處於工期遲延可體諒可補償之情況下（Excusable and Compensable Delay），則本研究之ABC其適用範圍如下： 1. 「變更設計」後，產生新增工項（Extra Work），並直接導致工期展延與間接成本之增加，排除單純之數量增減（Additional Work）。 2. 因可歸責業主之「工率降低」，導致工期展延的爭議（業主未要求趕工）。 3. 因「其他甲方因素」導致工期展延之情況（例如遲延簽發開工通知與工程停工等）。 Time burdens are almost always accompanied by increased costs. However, even an undisputed right by the contractor of entitlement to costs would be difficult to exercise unless those costs can be satisfactorily quantified and proven. The value of diligent recordkeeping cannot be over-stated and the method for quantifying the cost of delay is an imperative for most contractors. In practice, contractor’s delay claims against the owner have been pestered with unsatisfactory method of quantifying damages. Most common methods adopted by the courts include the “ratio” approach and the “actual disbursement” approach. Each of them possesses certain advantages over the other, yet none of them leads to realistic compensation. This work introduces an innovative method of cost accounting, namely Activity Based Costing (ABC), and investigates its potential into the realm of delay damages quantification. It is done by examining and comparing the reasoning in court rulings with a counterpart analysis by ABC. The result of the analysis is the basis for further inference. It is argued that by using ABC a contractor who presents a detailed breakdown of reasonable costs incurred during the delay period is a step closer to full and just recovery. The ABC method is useful for items which are conventionally difficult to prove and rule, such as salaries of the contractor’s officers performing general services at the home or branch offices, most capital expenses which cannot be allocated among jobs, or home office overhead which may be apportioned to a given project. It is suggested that a further development on Activity Based Management may be in need in order to provide useful assistance or information on cost categorization and management. Such services could be crucial if the contractor plans to undertake public works or other highly competed sectors.
