A person who never sends in a tax return does not stop a tax bill from being calculated. Under Internal Revenue Code Section 6020(b), the Internal Revenue Service can prepare a return on that person’s behalf using only the income already reported by employers, banks and other payers. The resulting document, called a substitute for return, carries legal weight in the collection system, but it is missing nearly everything that normally makes a real tax bill smaller than gross wages and 1099 income alone.
How a Substitute Return Gets Built From Third-Party Income Alone
The program that assembles these documents is the Automated Substitute for Return system, known internally as ASFR, and it runs entirely on data the IRS already holds on file: W-2 wages, 1099 payments, brokerage statements and similar third-party reporting. ASFR typically targets accounts where that reported income points to a meaningful tax liability and years have passed with no return on record. Because the system never sees a taxpayer’s actual paperwork, it has no way to apply a mortgage interest deduction, a business expense, a dependent, or a tax credit that would ordinarily reduce the amount owed.
The Treasury Inspector General for Tax Administration spelled out that limitation in a report dated August 26, 2026, stating that ASFR determinations are based only on income reported to the IRS and do not incorporate all deductions and credits to which taxpayers may be entitled. In practical terms, a substitute return almost always produces a larger balance due than the same person would owe by filing independently.
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Only Single or Separate: The Filing Status a Substitute Return Assumes
Filing status is where the gap widens further. The IRS’s own Automated Substitute for Return manual instructs the system to use only single or married-filing-separately status when it prepares the proposed assessment, regardless of a taxpayer’s actual household, according to the IRS’s Internal Revenue Manual section governing the ASFR program. A person who should have filed as head of household, or jointly with a spouse, gets none of the wider tax brackets or additional relief that status would have provided. Dependents, the Child Tax Credit and the Earned Income Tax Credit are absent for the same structural reason: the system has no way to confirm who lived in the household or who qualifies for what. Self-employment income fares no better, since the substitute calculation applies self-employment tax to the full reported amount without subtracting a single business expense.
The 30-Day Letter, Then the 90-Day Notice of Deficiency
A substitute return does not turn into a final bill overnight. ASFR first issues a 30-day letter proposing the tax, penalties and interest based on the third-party income alone. If there is no adequate response, the case advances to a Statutory Notice of Deficiency, generally delivered as a CP3219N notice, which gives the recipient 90 days to either file an actual return or petition the U.S. Tax Court before the proposed assessment becomes collectible. The IRS’s own notice guidance recommends filing a return at this stage to claim the deductions and expenses actually owed, and it specifies that a refund can only be paid if the return is filed within three years of that tax year’s original due date. Disputes of $50,000 or less per tax year can also use the Tax Court’s simplified small-case procedure rather than full litigation.
Why the Missing Deductions and Credits Raise the Number
The mechanics explain why a substitute return so often looks inflated next to a taxpayer’s own math. A freelancer whose only IRS-visible paper trail is a stack of 1099-NEC forms is taxed on the full gross amount, with no mileage, no home-office deduction and no cost of materials subtracted first. A retiree with several small pension and interest statements is taxed as a single filer with no medical-expense or mortgage-interest itemizing factored in at all, even where those items would have shrunk the bill considerably. None of this reflects a hidden penalty or bad faith on the IRS’s part; it reflects a system that can only see the income side of the ledger, never the expense or credit side, because that information only exists on a return nobody filed.
Filing a Real Return Still Reopens the Case
Nothing about a substitute return is permanent once it exists. Submitting an actual, signed return after the IRS has filed one under IRC 6020(b) generally replaces the substitute figures with the taxpayer’s own numbers, deductions and credits included, and the account is adjusted to reflect the corrected total rather than the third-party-only estimate ASFR started with. The IRS’s guidance on notices for unfiled returns confirms this directly, noting that it remains in a taxpayer’s interest to file a return and claim every exemption, credit and deduction to which the person is entitled even after a substitute assessment has already gone out. What a late-filed return does not undo are penalties already assessed for the late filing itself; those are calculated separately from the substitute’s income tax figure and generally survive the correction.
The Paperwork Left After a Substitute Return Closes
Replacing a substitute return with a real one settles what is owed, but it opens a second question right behind the first: whether an old refund is still recoverable and where a mailed correction actually stands with the IRS. Reversing an ASFR assessment fixes the tax calculation itself; it does not by itself track a case through the mail or confirm whether the three-year refund window described above is still open for a given tax year.
The IRS Refund Recovery Kit includes a refund status tracker spreadsheet and a plain explanation of the 3-year refund deadline that governs late-filed corrections.
Open the refund status tracker spreadsheet in The IRS Refund Recovery Kit.
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