Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of tax-prep whiz H&R Block (NYSE: HRB) were zapped by investors today as the stock sank as much as 10% in intraday trading after the company reported earnings.

So what: The fact that H&R Block reported a loss for the quarter shouldn't be surprising at all. As tax-preparation services constitute the bulk of the company's business, its revenue and profits are heavily weighted toward tax season and, specifically, its fiscal fourth quarter. For the fiscal first and second quarters -- ending in July and October, respectively -- business is slim pickings and the company often runs at a loss.

What investors are likely reacting to today, though, is not the loss itself, but the fact that the adjusted loss per share of $0.38 that the company reported was wider than the expected $0.34-per-share loss.

Now what: Great companies know what they're good at and they make the most of that expertise by sticking to it. H&R Block made the mistake of trying to get into too many adjacent business lines in recent years, and investors paid for that mistake by taking big losses on ill-advised ventures.

But the company has always been a solid presence in the tax-prep market, and it's now making an effort to refocus itself on that strength. Along with the fiscal fourth-quarter results, H&R Block also announced that it closed the sale of consulting arm RSM McGladrey, a deal that brought in $575 million and cut down on H&R Block's non-core businesses.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.