Have your taxes from previous years?  Archive them!  Collect all of your forms for each year, digitize them, and make sure they're backed up to the cloud—Google Drive, Dropbox, whatever.  The IRS can audit three to six years into the past and you can file a corrected return up to three years back, so make it a habit to keep this information organized.

Pieter Brueghel the Younger's The Tax Collector's Office, 1640.  I bet the IRS looks like this too.

If you're missing a year, or if you'd like to see what information the IRS has on your earnings for this or previous years, you can download tax account, income, and tax return transcripts online.  Just head over to the IRS transcript website and make an account!  Transcripts are free and can be downloaded immediately.  When you're doing your taxes for this year, this is an easy way to verify that you have all of the W-2s and 1099s that the IRS does.