Filing a 1040 violates the Fifth Amendment ONLY if doing so will subject you to CRIMINAL liability or if the information contained in the return could be used against you in a criminal trial.
For example, T has $100,000 in illegal drug sales. T must report the $100,000 of sales on a Schedule C as income from "sales" or from "sources I refuse to disclose" and may not deduct any expenses from the gross sales because the business is engaged in illegal activity. T then has to pay income & social security tax on the gross sales! The IRS cannot force T to tell them what was sold, nor can it force T to turn over any ledgers or books because doing so would force T to incriminate her/himself. However, without seeing a ledger, the IRS will argue that T underreported the income and may offer all kinds of evidence that T's standard of living would require income of $x and T reported less than $x. That's what the IRS did to Al Capone.
This post does not constitute legal advice, nor does it create an attorney-client relationship. Postings are based only on the information provided and you should consult an attorney in your area before relying on information contained in this post.