Order from ABC bill to X. Y. Z

We have received a work order for a project from ABC company.

Now we received a letter from ABC stating that

Ø Bank Guarantees for advance / performance is to be issued in the ABC

Ø Invoicing is to be raised on the four subsidiary / associates companies of ABC ON Pro rata basis:

W Ltd. 20%

X Ltd. 20%

Y Ltd. 50%

Z Ltd. 10%

Now do we need separate orders from these companies or the letter from the holding company is sufficient.

Plz give your valuable opinion.