Updated September 4, 2026. Quick answer: Idaho charges every S-corp a mandatory $20 minimum tax that a partnership-taxed LLC never owes at all, on top of the ordinary pass-through treatment both get.
Does this state require its own election
No separate Idaho filing exists to obtain S-corp status; the federal election controls. Idaho accepts the federal approval automatically; the corporation attaches a copy of it to its first Form 41S.
“Idaho accepts the federal approval of the S corporation election. Include a copy of the federal approval or a federal Form 2553 with your Form 41S the first year you file.”
Idaho State Tax Commission, S corporations guide
What it costs at the entity level
Idaho’s own Form 41S instructions state the $20 minimum tax applies to every S-corp; the partnership return, Form 65, carries no equivalent minimum-tax line at all.
| What Idaho charges | Figure |
|---|---|
| Rate | 6% on Idaho-apportioned excess net passive income or built-in gains, when either applies (a narrow, federally-mirrored case) |
| Minimum | $20 minimum tax required of every S corporation, plus a separate $10 Permanent Building Fund tax |
“The minimum tax of $20 is required for each corporation … This includes an S corporation.”
Idaho State Tax Commission, Form 41S instructions
The comparison against a plain LLC
The dollar gap is small, $20 a year, but it is unconditional: every Idaho S-corp owes it, in a loss year as much as a profit year, and a plain LLC filing Form 65 never sees the line at all.
What this does not model
This page does not model Idaho’s $10 Permanent Building Fund tax in detail beyond noting it exists alongside the $20 minimum.
No federal tax modelling is repeated here; see the federal S-corp election calculator for the payroll-tax and QBI mechanics this page assumes but does not recompute. No personal Idaho income tax on the pass-through income itself is modelled either.
Sources
Every figure on this page is read from the text quoted above, fetched directly from the state’s own site or code, as read on September 4, 2026.
| What it establishes | Source |
|---|---|
| Whether Idaho requires its own S-corp election | Idaho State Tax Commission, S corporations guide |
| What Idaho charges an S-corp at the entity level | Idaho State Tax Commission, Form 41S instructions |
General consumer information, not financial, tax or legal advice. State rules are as published by the cited source on September 4, 2026 and change; your own facts govern, and an S-corporation election is a decision to take with a tax professional who has seen your books.