At nearly 400 pages, the Treasury Department’s guidance for Section 409A of the tax code takes a long time to read. Time to comply with its new requirements, however, is in short supply.

Section 409A imposes complex new rules around how deferred compensation agreements should be structured if companies and executives want to avoid higher taxes. The effective date of the rule, already stalled for two years, is now Dec. 31—and compliance experts are pleading with the Internal Revenue Service yet again for more time.