According to the answer to this question: "How long should I keep my bills?", I should hold onto my taxes and supporting documents for 7 years.
Is this the right length of time? Unfortunately, my taxes tend to be complicated, and 7 years worth of tax returns are a bit of a burden. Is the basis for this number due to statute of limitations or something else?
How long you need to keep tax records will depend on jurisdiction. In general, if you discard records in a period of time less than your tax authority recommends, it may create audit problems down the road. ie: if you make a deduction supported by business expense receipts, and you discard those receipts next year, then you won't be able to defend the deduction if your tax authority audits you in 3 years.
Generally, how long you keep records would depend on: (a) how much time your tax authority has to audit you; and (b) how long after you file your return you are allowed to make your own amendments.
In your case (US-based), the IRS has straight-forward documentation about how long it expects you to keep records:
https://www.irs.gov/businesses/small-businesses-self-employed/how-long-should-i-keep-records
Period of Limitations that apply to income tax returns
Keep records for 3 years if situations (4), (5), and (6) below do not apply to you.
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.
Keep records for 7 years if you file a claim for a loss from worthless securities or bad debt deduction.
Keep records for 6 years if you do not report income that you should report, and it is more than 25% of the gross income shown on your return.
Keep records indefinitely if you do not file a return.
Keep records indefinitely if you file a fraudulent return.
Keep employment tax records for at least 4 years after the date that the tax becomes due or is paid, whichever is later.
Note that the above are the minimum periods to keep records; for your own purposes you may want to keep them for longer periods than that. For example, you may be in a position to discover that you would like to refile a prior tax return, because you forgot to claim a tax credit that was available to you. If you would have been eligible to refile in that period but no longer have documentation, you are out of luck.
Unfortunately, my taxes tend to be complicated
This. In and of itself, is a greater reason to keep the documents. The other answer offered a good summary, but keep in mind, if the IRS decides you fraudulently withheld claiming income, they can go back 7 years.
I bought a rental property in 1987, and sold it in 2016. In that case, keeping the returns seemed the right thing to do to have the paper trail for basis, else I could claim anything, and hope for the best.
I have all my tax returns since my first tax return, 1980. It's one drawer of a file cabinet. Not too great a burden.
