There was a time not so long ago when authors never had to worry about handing in their manuscripts on time. Deadlines back then were a formality—something publishers took about as seriously in the course of contractual negotiations as they did the profit-and-loss statements they used to justify their acquisitions. If an author hit their delivery date, great! But if they didn’t, that was O.K., too.

For the most part, that is still true. But as book sales fall and publishing houses look for ways to cut costs, many literary agents are growing increasingly worried that publishers looking to trim their lists will start holding authors to deadlines and using lateness as an occasion to renegotiate advances and, in some cases, terminate contracts altogether.

“Publishers are looking at their books and saying, ‘O.K., this book is two years late. Do we want it anymore?’” said Eric Simonoff, an agent at WME Entertainment. “If the answer is no, they’re saying, ‘We don’t want it anymore—we’re calling our loan.’”

He went on: “Sometimes people have buyer’s remorse, and it’s a very convenient way of rectifying your buyer’s remorse after the fact. It’s safe to say that delivery dates are more meaningful now than they ever have been before. I think everyone’s putting their clients on notice and saying, ‘This is serious.’”

Most publishers are well acquainted with the feeling of regret that comes with realizing that a book they signed up years ago is no longer worth publishing. Sometimes this happens because the subject of the book has become irrelevant or the market for it has become oversaturated. Sometimes it happens because the editor who bought it has left or been fired. Other times it’s because the sum that was paid for the book at the point of acquisition has come to seem exorbitant and ridiculous.

Historically, such regrets have led to action only in rare circumstances, as the practice of canceling contracts has been regarded in the industry as supremely unsavory and damaging. Publishers by and large have been unwilling to risk earning a reputation among literary agents as being mercurial and untrustworthy. (To this day, agents bristle when reminded of the great purge of HarperCollins, when in the summer of 1997 CEO Anthea Disney ordered 100 books canceled in an effort to “clean house.”)

But like so many other practices associated with the “gentleman’s business” that the book business used to be, eating advances in the service of good humor has become a luxury most publishers do not indulge in as readily as they once did.

“What has happened is that in the cold light of morning, publishers are looking at all these expensive deals they made based on the inflated marketplace, and now the bill is coming due and they don’t want the contracts anymore,” said one top agent, who spoke on the condition of anonymity. “I buttoned up all my contracts—I amended all of them way before the due dates came. Once the author delivers on time, then the publisher has to find something unacceptable in form and content, and that’s a much more serious thing to do. At that point there’s a whole process that they have to go through, and it’s much more challenging for them to find something in breach.”

As a result, authors are under unprecedented pressure from their agents to stay on schedule. Most of the literary agents interviewed for this article said they have tried to impress on their clients that if they want to make sure they don’t lose their contracts and find themselves having to pay back an advance that in many cases they’ve already spent, they had better be vigilant about turning their manuscripts in on time.

“I don’t want my authors to be in that situation, so I’ve been reminding them all year long to not treat their deadlines lightly,” said the independent agent David Kuhn. “Everyone’s paying attention to their contracted deadlines more than they used to, for sure—at least publishers are, and therefore agents are, and therefore authors should.”

“Publishers are going to look at every opportunity to save money in this climate,” said Simon Lipskar, an agent at Writers House. “Most of them aren’t being quite as venal as calling to cancel a day after the due date, but my standard recommendation to my authors at this time is to just deliver their books on schedule.” In so doing, Mr. Lipskar said, “they remove one major contractual ‘out’ for the publishers.”

None of the agents interviewed for this story would provide actual examples of late books that have been canceled recently on the basis of late delivery, even as they asserted with total confidence that the practice is becoming more common. Many noted that cancellations are so traumatic and embarrassing for everyone involved that extra care is taken to prevent them becoming gossip fodder.

Publishers, for their part, aren’t copping to the charge (at least not when The Observer asks them about it), and while many of the editors and executives reached for this story said they’d heard about other houses canceling books because they were late, all of them emphasized that they themselves had not been party to any such incidents.

Speaking on background, though, one publishing executive at a New York house confirmed agents’ fears, saying that authors—especially those without a rock-solid reputation—must be conscientious about honoring their contracts if they want to avoid the possibility of having to pay back their advance.

“People ruin their writing careers by not taking this stuff seriously,” the executive said. “Usually they decide to take legal advice from some friend who says the publisher will never ask for the money back. Well, they frequently do. And nowadays, repaying the publisher is going to be harder, because a writer can’t get the money from Condé Nast. Now is the time for you to be really nice to your publisher.”

The executive said the best thing authors who are having trouble can do is be honest with their editors about their progress (or lack thereof), thus avoiding a situation in which a publisher has budgeted for a book on the assumption that it would come in on time.

“Even if you’re late, be collaborative and communicative,” the executive said. “We just need to know what’s going on, and if it’s not coming, we need to know. Because, you know what, sometimes people have trouble, and we can help. But often when authors know they’re late and they know they’re in trouble, they hide. And that’s exactly the wrong thing to do.”

Of course, authors with established track records and promising projects in the works don’t have much to worry about. Spiegel & Grau won’t be dropping Sara Gruen’s long-delayed Ape House anytime soon, just as Doubleday was never going to cancel Dan Brown’s follow-up to The Da Vinci Code.

As Mr. Simonoff said, “The reality is, you don’t have to worry about lateness if they want your book. You only have to worry about lateness if they don’t.”

lneyfakh@observer.com