If the capital goods go through the customs clearance in several steps, how does one confirm the completion of the process?

In principle, the confirmation of completing investment in kind is issued when the import of the capital good is completed.
If the capital goods are imported in steps, then the confirmation is issued after the last customs clearance was processed for all capital goods.
However, if the introduced price of capital goods is relatively high, the confirmation can be issued exceptionally. (for example: first part of capital goods are imported in March, 2005 and the second part of the capital goods are imported in June, 2006)