Many supplies of goods and services made consist of several elements combined in a single transaction. Where such supplies occur, it is necessary for the supplier to determine whether they are making two (or more) ‘multiple’ supplies or a single ‘composite’ supply combining all elements.
Source: gccfintax.com
For a recent explanation of the EU rules (by the AG of the European Court of Justice), please see this POST. Other posts with the topic composite supplies can be found HERE.