Rough day for H&R Block.

H&R Block Inc.'s (HRB - Get Report)  day just got worse as the company suffered the largest single-day drop in its stock price in over three decades.

The company's stock fell $5.37, or 18%, to $24.22 in trading on Wednesday after the tax-preparation company released a 2019 revenue outlook yesterday that failed to meet analysts' expectations. Earlier the shares fell as much as $5.67, or 19.2%, to $23.33, the lowest in the past 52 weeks, and the worst since the stock lost 20% on Oct. 19, 1987.

Kansas City-based H&R Block said it expects revenue will be between $3.05 and $3.1 billion in 2019, compared with analysts' estimates of $3.14 billion, according to Bloomberg data, as it plans on adjusting its prices for its products and services ahead of the implementation of new tax reforms in 2019. These reforms would make filing returns simpler and cheaper, which does not bode well for a company that charges customers based on the complexity of their filings.

H&R Block reported 2017 fourth quarter earnings that beat analysts' expectations. Net income came in at $1.1 billion, up 46% from the same period in 2016. The company's earnings were bolstered by tax cuts as its own income tax bill fell by 80% from $425 million in 2016 to $85 million in 2017.

Management caught investors and analysts off-guard by unexpectedly providing details of the company's plans for 2019 - a discussion they usually have during December, right ahead of tax season - during the company's conference call Tuesday.

Analysts have slashed their estimates for share earnings by more than 10% for 2019 amid concerns of H&R Block's investment strategy for the next year. Morgan Stanley's Thomas Allen cut his expectations from $2.34 per share to $2.02 as the firm remains skeptical of H&R Block's "volatile track record of results and lack of visibility into if management's initiatives will pay off," according to a note.

CEO Jeffrey Jones said that 2019 would be an investment year for H&R Block. H&R Block plans to modernize its tech platforms in an effort to be more accessible to customers, Jones said.

"Consumer expectations about how they seek and want help from H&R Block are constantly evolving, and we need consumer-facing products that not only meets, but exceeds consumer expectations," Jones said.