"substantial customer" is correct and usable in written English.
You can use it to refer to a customer that purchases a large amount of goods or services on a regular basis. For example, "Our company has experienced considerable growth this quarter due to our substantial customers."
John S. Riccitiello, the president of Electronic Arts, said that for EA.com to attract a substantial customer base, the game must truly appeal to a mainstream audience even more so than it currently does.
Wildfire has built a substantial customer base but now needs to figure out how to monetize them better.
It offers startups access to its executives for advice, its marketing clout and introduces these young companies to Workday's substantial customer base.
Banks know they don't need to be better than the fintech companies; their advantages of scale and distribution ensure they can maintain their substantial customer base with a sufficient product.
Both wanted a new location with substantial customer traffic, and they considered places such as Hollywood and Burbank.
Large ISPs like EarthLink Inc., MindSpring Inc. and America Online Inc. provide dial-up Internet service to a substantial customer base.
In recent years the famously litigious Yuen sued the only other interactive guides that had substantial customers.
"In short," says Osha, "CompactFlash has won, and we believe investors should not be concerned by the proliferation of competing claims from memory card makers unless they see design wins at substantial customers, which has yet to happen".
There are substantial strategic customer advantages for both Critical Path and ShoZu customers from this acquisition.
The advice was first-rate, and the results have already triggered talks with a substantial future customer".
The trustee's report concludes there was a substantial "shortfall" in customer segregated funds every day from Oct. 26, when $615 million in loans from customer accounts were not repaid, until MF Global filed for bankruptcy on Oct. 31.
