The Securities and Exchange Commission’s new roadmap has given accounting experts and companies a reason to exhale. Now, at last, everyone knows the SEC’s vision and likely deadlines for moving the U.S. onto global accounting standards.

However, as accounting firms caution, that sigh of relief will be fleeting as finance and accounting teams in the U.S. begin to review all the work that would need to get done if the SEC continues on the path to international financial reporting standards — which would require all U.S. publicly traded companies to use IFRS by 2016. Converting to another accounting language will involve, among other changes, an extensive review and possible revamping of IT systems and accounting policies and procedures, as well as employee training and evaluations of possible tax implications.

Even though the SEC’s eight-year plan is considered “proposed” and carries with it several contingent steps, it has given the accounting firms credence to continue encouraging companies to take IFRS seriously, as they have been doing for the past several months. U.S. companies need to start thinking about what the SEC’s plan means to them “and exactly how long it will take for them to get through everything and meet those deadlines,” says DJ Gannon, a partner at Deloitte & Touche.

PricewaterhouseCoopers is also encouraging clients to begin thinking about IFRS now. “Early action will allow companies to control costs, understand and manage the challenging scope of implementation, and ensure a smooth transition plan,” the firm wrote in its IFRS implementation guide.

When they unveiled their roadmap, the SEC commissioners talked about a potential — “mandate” — which is the only way companies will start paying attention, opined Big Four auditors. Under the plan, the SEC will decide in 2011 whether to require all of its registrants to use IFRS. “We heard from many parties that if the U.S. is to move toward IFRS, we need to work toward a date certain,” added SEC chief accountant Conrad Hewitt.

Assuming the SEC keeps the same timetable as the one introduced Wednesday, the “date certain” is 2016, which is when all companies, big and small, would begin using IFRS. The expected deadline for large companies is 2014, and early adopters — the largest of the U.S. multinationals measured by industry — could choose to begin using IFRS to report financial results starting in 2010.

To be sure, large multinationals have begun to look at what filing under IFRS would mean for them. One obvious benefit is that they could cut back on the systems and departments that support U.S. generally accepted accounting principles, and rely more on the IFRS backbone that already exists in foreign subsidiaries. That’s similar to what happened at foreign companies already using IFRS when the SEC eliminated the GAAP-reconciliation requirement last year.

Big Four firms believe the SEC’s proposal puts the United States closer to using the same accounting language as more than 100 countries. “Disparate accounting standards benefit no one,” said James Turley, chairman and CEO of Ernst & Young. “A change to a common global accounting language will benefit investors and market efficiency by increasing the transparency and comparability of information.”

Added PricewaterhouseCoopers chairman and senior partner Dennis Nally, “international financial reporting standards represents the best opportunity to achieve the goal of a single set of high-quality because of its current widespread use outside of the U.S.”

The SEC’s thrust into IFRS stems from its vision to provide investors with greater comparability when examining financial statements, regardless of what country the company calls home. “We realize significant work lies ahead in preparing for a transition, but believe IFRS has proven to be a reputable set of standards for preparing transparent information,” said Cindy Fornelli, executive director of the Center for Audit Quality, an industry group that represents more than 800 firms.

From a practical perspective, companies should be thinking about several key areas, noted KPMG partner Janice Patrisso in a webcast held on Thursday. She recommended that companies focus on the timeline, and where their company fits into the scheme, as well as SEC’s requirement to produce three-year’s worth of U.S. GAAP results to support the first IFRS filing.

Companies have to realize that a shift to IFRS “impacts the business at large,” emphasized Patrisso. Indeed, in the accounting and finance department, companies will have to do a GAAP analysis and identify disclosure requirements, revise their chart of accounts, and figure out what new accounting policies and processes have to be implemented. “The devil is in the details,” she said.

Also, companies will have to “synchronize” IFRS implementation efforts into other major projects. For instance, a new enterprise resource planning system implementation will require new data and tax reporting requirements related to IFRS. What’s more, companies will have to renegotiate debt agreements and business contracts that use U.S. GAAP terminology. “Everyone will need to be educated [with respect to IFRS] while still going along with business as usual. So it’s important to start early,” asserts Patrisso.