What is the 5498 form and why I am receiving it after April 15th?

The 5498 form details your IRA contributions for the previous tax year, including your regular contributions, rollover, and direct transfer contributions. Since you are able to make regular contributions to your IRA for the previous year up until April 15th of the current year, the 5498 forms are not generated until after that date. 

If you made contributions to your IRA for the tax year, you would include that information when you file your taxes. The 5498 form is provided for your records. You are not required to include the form with your taxes.