What do I do if I haven't filed any w2 from 2016 to 2020 and can't get a response from past employers to retrieve them?

Well.....you have now forfeited any refund you could have received for 2016 and if you do not file 2017 by May 17 you forfeit that refund too.   If you owe tax the IRS still wants to be paid though.

What if I do not file my tax return?

https://ttlc.intuit.com/questions/2572308-what-happens-if-i-don-t-file-my-taxes

W-2's come from employers.   It is unclear how much effort you have put into getting those W-2's.

You might need to phone, drop in, email and/or snail mail an old employer to make sure they know where to send your W-2.

https://ttlc.intuit.com/questions/2561916-how-can-i-get-a-copy-of-my-w-2

Other ways to get W-2’s:

Pay Social Security $90 per W-2:

https://www.irs.gov/help-resources/tools-faqs/faqs-for-individuals/frequently-asked-tax-questions-answers/irs-procedures/transcript-or-copy-of-form-w-2/transcript-or-copy-of-form-w-2

You can get a wage and income transcript from the IRS:  It will not show the actual W-2, 1099’s, etc, but will show the income information the IRS received.  It will not, however, show your state information. It will only show the federal information.

https://www.irs.gov/individuals/get-transcript

Each tax year has to be filed separately using the forms for the specific tax year.  They cannot be combined in any way--do not even put them in the same envelope when you mail them.  Software for past years is available back to 2017.  Any earlier years can only be prepared on paper forms by hand--and those refunds have been forfeited now.

The current online program can only be used for a 2020 return--no other year.  And if you did not file a 2019 return you will have trouble e-filing 2020.  When it asks for your 2019 AGI try using zero.  If zero does not work then you have to print, sign and mail 2020.

Online preparation and e-filing for 2017, 2018 and 2019 is permanently closed.

To file a return for a prior tax year

 If you need to prepare a return for 2017, 2018, or 2019 you can purchase and download desktop software to do it, then print, sign,  and mail the return(s)

https://turbotax.intuit.com/personal-taxes/past-years-products/

You may also want to explore purchasing the software from various retailers such as Amazon, Costco, Best Buy, Walmart, Sam’s, etc.

Remember to prepare your state return as well—if you live in a state that has a state income tax.

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.

Note:  The desktop software you need to prepare the prior year return must be installed/downloaded to a full PC or Mac.  It cannot be used on a mobile device.

If you are getting a refund, there is not a penalty for filing past the deadline.  If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.

Refunds for tax years 2016 or earlier have been forfeited and will not be paid to you even if shown on the tax return form.  But if you owe tax due, you will still have to pay, and you will be billed later for the interest and penalties owed.

You might need to seek local paid tax help to get your tax situation sorted out, especially if you owe.  A tax pro will know how to negotiate with the IRS.