General Form 5500 due date
Plan sponsors generally file a Form 5500-series annual return/report by the last day of the seventh month after the plan year ends. For a calendar-year plan, that normally means July 31.
Calendar-year example
For a plan year ending December 31, the normal filing date is generally July 31 of the following year. If the date falls on a weekend or legal holiday, confirm the applicable filing-day rule in the current instructions.
Form 5558 extension
A timely Form 5558 can provide a one-time extension. The current Form 5558 instructions allow an extension generally up to the 15th day of the third month after the normal due date. File the extension request on or before the normal due date.
Special relief
Disaster declarations, combat-zone rules and other agency relief can affect deadlines. Do not assume a general extension applies; confirm the specific IRS/DOL notice for the filer and location.