If you’re taking on a very large job, you may choose to spread the work over several subsidiary companies within your family of companies. One reason to use different companies is to limit liability to the company that holds the contract. You may also have companies that specialize in different kinds of work, such as electrical, plumbing, fabrication, or equipment. If all these companies are doing work on the same job, you need to allocate revenue and expenses between the various companies. You can use intercompany invoicing between the companies to do this.