You can, but it would be a good idea to keep the program on your computer (if you're using the Desktop program) in case you need to amend your return, or if you just recently filed and the return was rejected, you can edit the return and re-file as long as you have the desktop program.
If you filed using TurboTax Online you will want to make sure you download a copy of the tax return and keep for your records.
From the IRS website:
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Keep records for 3 years from the date you filed your original return or 2 years from the date you paid the tax, whichever is later, if you file a claim for credit or refund after you file your return.
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Keep records for 7 years if you file a claim for a loss from worthless securities or bad debt deduction.