The phrase "a substantial debt" is correct and usable in written English.
It can be used when referring to a significant amount of money that is owed or required to be paid back.
Example: "After years of overspending, she found herself facing a substantial debt that she struggled to manage."
Alternatives: "a significant debt" or "a considerable debt".
You have to understand, this is why Yale University has a substantial debt, and why the City of New Haven has a substantial debt.
True, it owes a substantial debt to the documentary realism of Ken Loach.
"When they become graduates they will become people with a substantial debt to repay – or not repay".
Although Mapletown's community hospital is operating in the black, it carries a substantial debt load and its future in the changing health care environment is uncertain.
The sound and visuals owed a substantial debt to David Bowie's Berlin trilogy and his stranded alien in The Man Who Fell To Earth.
The Beatles were not alone in imitating the Everlys' sound; Britain's Hollies and America's Simon and Garfunkel also owed the Kentucky brothers a substantial debt.
"Households are clearly in a very substantial debt hole and looking at the prospect of borrowing on more expensive terms in the future," said Tom Schlesinger, executive director of the Financial Markets Center, a nonprofit research group in Philomont, Va.
To him, all of us who have worked within or alongside this framework owe a very substantial debt; and that is something which I personally find pleasure in acknowledging with gratitude.
Every new superstar DJ with huge LED shows, massive riffs and vertiginous drops, and most of all Skrillex, owes them a very substantial debt. .
And with stock prices so depressed, even an investor taking on substantial debt for a buyout can still make the numbers work.
The result was a profitable season last year and a chipping away at substantial debt.
