Cobweb of sister concerns

Respected Sir 

A family owns a cobweb of complex Chain of multiple LLPs & a single Pvt Ltd Co. This Co owns Factory and manufactures equipments and sells only to family owned LLPs, who in turn export.  At back end, Ltd Co raises Invoices on LLPs, who makes a big kill in export market. Profit margin is

 3-400%. Rarely Customs want to see Purchasing Invoices from LLPs.

Is there any accounting, Customs, taxation trap/ loose ends?

Kindly guide

Regards