1120-S Late Filing Penalty Amount and Calculation

Quick answer: For a Form 1120-S (S corporation return) filed late, the penalty is $195 per month (adjusted for inflation) times the number of shareholders, capped at 12 months — this is separate from, and in addition to, any income tax due. If it isn't filed for two full years, the penalty caps out at 12 months for each year's late return, so each unfiled year generates its own separate, maxed-out penalty; it does not keep growing indefinitely on a single return. This answer assumes current-year rules; confirm the exact inflation-adjusted dollar figure for the specific tax year, since the base $195 rate adjusts annually.

What it is

The specific penalty for a late-filed S corporation return is governed by IRC § 6699, not the general corporate late-filing penalty in IRC § 6651(a) that applies to C corporations. Publication 542's late-filing discussion (5% per month, up to 25%) describes the general corporate penalty on unpaid tax, but S corporations are typically pass-through entities with little or no tax due at the entity level — so Congress created a separate, flat per-shareholder penalty instead.

How it works

Under IRC § 6699(a), if an S corporation required to file a return under section 6037 fails to file such return at the time prescribed therefor (determined with regard to any extension of time for filing), or files a return which fails to show the information required under section 6037, such S corporation shall be liable for a penalty determined under subsection (b) for each month (or fraction thereof) during which such failure continues (but not to exceed 12 months), unless it is shown that such failure is due to reasonable cause.¹

The dollar amount is set by § 6699(b): the amount determined under this subsection for any month is the product of $195, multiplied by the number of persons who were shareholders in the S corporation during any part of the taxable year.² That $195 base figure is indexed for inflation: in the case of any return required to be filed in a calendar year beginning after 2014, the $195 dollar amount under subsection (b)(1) shall be increased by an amount equal to such dollar amount multiplied by the cost-of-living adjustment³, and any adjusted figure is rounded to the next lowest multiple of $5⁴. So confirm the current inflation-adjusted per-shareholder, per-month amount for the specific tax year involved rather than assuming $195 flat.

Procedurally, this penalty is assessed directly against the S corporation without going through the normal deficiency process: the penalty imposed by subsection (a) shall be assessed against the S corporation, and Subchapter B of chapter 63 (relating to deficiency procedures for income, estate, gift, and certain excise taxes) shall not apply in respect of the assessment or collection of any penalty imposed by subsection (a).⁵

Example (illustrative)

Say an S corp has 4 shareholders and files its return 5 months late, with no reasonable cause. Using $195/month: 4 shareholders × $195 × 5 months = $3,900. If the return is more than 12 months late, the penalty simply stops accruing at the 12-month cap — 4 × $195 × 12 = $9,360 — it doesn't keep climbing.

Risks and limits — the two-year scenario

Because § 6699(a) caps the penalty at 12 months per required return, failing to file for two separate tax years means two separate returns are each late, and each one independently accrues its own penalty up to its own 12-month cap. There isn't a single continuous penalty that runs for 24 months on one return — instead you'd generally face two maxed-out § 6699 penalties (one for each year's Form 1120-S), unless reasonable cause is shown for either year.

Two additional risks compound this:

• Reasonable cause is the only escape. The penalty won't apply if the corporation can show the failure was due to reasonable cause.
• This is separate from other consequences. If the corporation's S status affects individual shareholders' tax reporting (via K-1s), unfiled returns can delay shareholder filings and create their own downstream issues, and if any entity-level tax is also owed, other penalties (accuracy-related penalties under § 6662, discussed in Publication 542, or trust fund recovery penalties for unpaid withholding) could layer on top.

In practice

The § 6699 penalty is a flat, shareholder-count-driven penalty designed to compensate for the fact that S corps usually don't owe entity-level income tax — it doesn't wipe away or reduce any tax owed, and it accrues per return, per year, up to 12 months each. Multiple unfiled years mean multiple separate exposures.

Given the two-year gap and multiple potential penalty layers here, this is a good time to sit down with a CPA to sort out exactly which returns, penalties, and reasonable-cause arguments apply to the specific years involved.