A 5498 is issued by the brokerage or account agent when a retirement account has had new money In (not growth or earnings). That money that is newly contributed or otherwise rolled/transferred in. It isn't a tax document, and you do not enter it anywhere. It's informational. You review it to confirm the amount and for the tax year noted, is as intended, and is what they are reporting they did with it. You also might use the year ending balance as part of data you enter for form 8606 or IRS worksheets for purposes of reporting that info in conjunction with 1099-R forms.