Form 5498 is not a Tax Form. It isn't used to prepare and file income taxes. It is used for you to confirm what your taxpayer client did, from the perspective of a retirement account into which they apparently made some sort of contribution or rollover or conversion, for some tax year that they need to tell you about. They need to tell you what they did, what it represents. The form is part of due diligence of the amount.

Did they earn money as Sched C, or as an employee, or make a rollover or make a conversion? Is it for the tax year you are working on? What else do they participate in for retirement, such as 401(k) at work? If they expect this to be deductible, you need to confirm it went into a Trad IRA type of account and that they qualify for that activity. How old are they?

You have some more work to do.