Can i work on multiple tax years at one time. I need to complete 2017,2018,2018 &2020 for my small business

[xmasbaby0]

No.   Each tax year is separate.   Do not try to combine them in any way--do not even mail two years in the same envelope.

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.

[SweetieJean]

Is your small business an S Corp, C Corp or Partnership?  If so, you need to use TT Business, which is only available as a Windows desktop.

[Mike9241]

you should be preparing the returns in chronological order.  the reason is that if you do this, necessary info from 2017 will transfer to 2018 and then 2018 to 2019

if you're using online for 2020 you will need to download the .tax2019 file to your online a/c so the info transfers.

[librewolf]

To second Champ's info. If you start with the oldest return and complete it, when you start the next year's Turbo tax will pull info from 2017 for your 2018 return. That way you are not starting from scratch for each year.