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 | 5.3% (tax year 2025) 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.
Figures verified against the Idaho State Tax Commission S corporations guide and Form 41S instructions (tax year 2025 edition) on September 30, 2026; the Form 65 comparison was not re-checked.
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.