It is recommended to bring one's tax transcript for the past 5 years (or 3 years if naturalization via marriage) to the US naturalization interview. How does one get one's tax transcript for the 5th year for the US Naturalization process? https://www.irs.gov/individuals/get-transcript only has the past 4 years.
This IRS FAQ page says:
Q5. How do I request a transcript for an older tax year when it's not available online?
Tax return and record of account transcripts are only available for the current tax year and three prior tax years when using Get Transcript Online. Note: There is a "show all +" expand button below the online tax account transcript type that may provide additional tax years you need. Otherwise, you must submit Form 4506-T to request a transcript for a tax year not available.
Tax return and tax account transcripts are also limited to the current and prior three tax years when using Get Transcript by Mail. To get older tax account transcripts, submit Form 4506-T.
Thus, if the tax transcript you want isn't listed, and doesn't appear when the "show all +" expand button is toggled, submit Form 4506-T to request a transcript for a tax year not available.
As backup, you might bring with you an actual, physical copy of your US tax return for the year in question.