The system of allocation of cost generates them of the ABC model is defined to two stages. Just in reference to the costs it generates them can be identified some meaningful innovations in the allocation process.
In the first place the costs generate them do not come group to you for centers of cost ²¹ , which often can be wide and not homogenous, but for activity.
It is important to hold account of the fact that the activities in ABC logic are the result of a process that can be involved more organizational unit.
The criteria of selection of the activities differ from those of the cost centers and make reference more to turn out you of the same activity that to the organizational structure.
Being based on the idea that all costs are variable, it achieves some that reducing I use it of one of one given activity reduce the consumptions of resources to it connects to you.
The costs of the various activities come puttinges in relation with of the specific determining factors (activity cost driver). Activities tied to the same factor, or factors between they correlate to you, come grouped in only pool ²² and allotted on the products or lines of product on the base of specific the common determining factor.

Figure 3.1: accounting method of ABC type Source: www.unitec.it

The activity driver they measure the frequency and the intensity of employment of an activity from part of a cost object and can represent in such sense the output of an activity ²³ .
Choice of these driver is phase a lot important, that it determines the good operation of the accounting method being those factors that determine a change in the amount of the costs of an activity, therefore, to the ends of the continuous improvement is necessary to characterize a disaggregazione more analytics of the activities that concurs to render the possible determinants of the level of consumption of resources evident.
The applications of the method can be rendered impraticabile if an elevated number of cost is adopted too much driver, necessarily must bring of the simplifications even if these imply one smaller analiticità in the definition of the activities.
Moreover even if it is certain that a greater number of cost driver involves a greater accuracy of the information, this can reduce the comprensibilità of the system of calculation of the costs and of it it renders the use difficult.
In the choice of driver the more important account of the existence of one must be held in the first place correlation between activity cost driver and the effective consumption of resources employed in the activity.
The existence of the correlation above all assumes greater relief in an optical of along period, since the costs of the various activities are often fixed in the short period re-entering in kind in the structure costs.
Moreover the facility in obtaining must be considered gives you for the calculation of the costs by means of the employment of the cost driver.
This aspect regards the cost of the surveys that affects the opportunity deeply to adopt an ABC system.
Finally, it must keep in mind the effects caused from I use of the specific one cost driver, in how much, the introduction of an accounting method involves of the consequences on the plan of the behavior of all the Decision-Making Centers that use the information, especially if they are inserted in an control system of management.

• Note 21: several they are the definitions of cost center: "unità operativa" definita in funzione delle esigenze conoscitive ed operative di una determinazione sistematica dei costi ad essa afferenti(Tail, 1968); aree di responsabilità in grado di influenzare in via diretta solo i costi (e non, ad esempio, i ricavi) (Brusa and Dezzani, 1983); gruppi di operazioni o di processi che configurano dei centri operativi, ai quali possono essere attribuiti particolari raggruppamenti di costi> (Selleri, 1990)
• Note 22: Grouping of homogenous costs
• Note 23: CINQUINI L. (2003) Instruments for the cost analysis, Vol I, Giappichelli Publisher, Turin.