HOW LONG SHOULD I KEEP COPIES OF MY TAX RETURNS, AND WHAT DO I DO IF I DIDN’T KEEP A COPY AND NOW I NEED ONE

On the subject of tax returns, the IRS recently released a “Tax Tip” (IRS Tax Tip 2018-90, June 12, 2018) that says the IRS “recommends that taxpayers keep a copy of tax returns for at least three years.”  It also provides useful information on how to get a transcript of a tax return if you need one (for some purposes you can actually be required to provide a transcript rather than a copy of the return), and how to get a copy of your return if you don’t have one.  
Beware, however: the IRS says keep those old returns for at least three years.  There are situations where you may need copies of your returns, and other records, going back as long as seven years, or more.