Which statement is false about custom calculation rules?

The statement asserting that custom calculation rules cannot have defined destination members is false because custom calculation rules indeed allow for the definition of destination members. In the context of Profitability and Cost Management Cloud (PCMCS), these rules are integral for managing how calculated values are stored and reported.

Custom calculation rules can be set up to target specific destination members, meaning that when an adjustment or computation is made, it can be directed at a defined set of data points or categories where the results should be stored. This capacity facilitates precise modeling of financial scenarios and enhances the analytics capabilities within the PCMCS environment.

In contrast, the other statements are accurate. Custom calculation rules do utilize formulas in MDX format, which is essential for crafting sophisticated calculations and data manipulations within multidimensional databases. Additionally, they do contain aspects for defining a driver basis and an accounting offset, which are vital for accurate financial reporting and analysis. Lastly, these rules are indeed used primarily for adjusting existing data to create various financial scenarios, further demonstrating their flexibility and utility in financial modeling.