Illinois Condominium Quorum & Supermajority Calculator

How this calculator works

This is a quorum-and-threshold validator for Illinois condominium unit-owner votes. Given the total unit owners, in-person attendance, proxy count, vote type, and any declaration-specified overrides, it returns:

1. Whether quorum has been met (total attendance compared against the effective quorum requirement under 765 ILCS 605/18(a)(8) or the declaration-specified override).
2. The yes votes required to pass for the vote type (75% of total ownership for declaration amendments under § 27; majority of those present for board removal under § 18.4; etc.).
3. The current ballot status (PASSED, FAILED, PENDING, or NO-QUORUM) based on the supplied vote tally.

Use the calculator before convening a unit-owner meeting to confirm the procedural framework; use it during ballot counting to validate the threshold; use it after a meeting to memorialize the outcome in the secretary's minutes.

The relevant Illinois Condominium Property Act statute

Illinois condominium voting is governed by the Condominium Property Act (765 ILCS 605):

765 ILCS 605/18(a)(8) — Quorum for unit-owner meetings is 20% of the unit owners (by percentage of undivided ownership interest in the common elements) unless the declaration specifies a HIGHER threshold. The 20% is a STATUTORY FLOOR — a declaration cannot specify a quorum lower than 20%.

765 ILCS 605/18(a)(9) — Board and unit-owner meeting notice requirements (10-30 day notice for owner meetings; 48-hour notice for board meetings). Addressed in detail by the companion board-meeting notice calculator.

765 ILCS 605/18.4 — Powers and duties of the board. Section 18.4 includes the procedure for board removal: a special meeting of unit owners called for the purpose, with removal by majority vote of the unit owners present at a meeting where a quorum is established.

765 ILCS 605/27 — Declaration amendment. Default requirement is approval by unit owners holding NOT LESS THAN 75% of the undivided ownership interest in the common elements, unless the declaration specifies a higher threshold. The 75% is a STATUTORY FLOOR.

765 ILCS 605/27(b) — Amendments that create rights or obligations of the developer require developer consent.

765 ILCS 605/18(a)(8) — Bylaws may specify the manner of allocating votes among unit owners — typically by percentage of undivided interest in the common elements. Per-unit-vote allocation is also permitted if the declaration so specifies.

Key thresholds and gotchas

MAJORITY OF TOTAL OWNERSHIP vs MAJORITY OF THOSE PRESENT. The two thresholds produce different outcomes when turnout is low. Illinois uses MAJORITY OF TOTAL OWNERSHIP for declaration amendments (§ 27, 75% threshold) — the property-rights actions. Illinois uses MAJORITY OF THOSE PRESENT for board removal (§ 18.4) and regular business — the governance actions. Confusing the two is a common voting-threshold error.

A declaration amendment can fail even with 90% of voters approving. In a 100-unit association with 60 voters (60% turnout), 54 yes votes (90% of voters) is below the 75-vote total-ownership threshold and the amendment FAILS. The 75% threshold is on TOTAL ownership, not voters.

The 20% quorum is a STATUTORY FLOOR. A declaration specifying 15% quorum is unenforceable to the extent it falls below the 20% floor. Declarations may specify HIGHER quorum (30%, 50%, 75%); they cannot specify lower.

The 75% declaration-amendment threshold is also a FLOOR. A declaration provision specifying 51% for declaration amendments is unenforceable to the extent it falls below the 75% floor. The legislature set 75% as the minimum because declaration amendments alter property rights of every owner.

Proxies count once for quorum, once for the vote tally. A valid Illinois proxy must be in writing, signed, and delivered before the meeting starts. Many declarations specify a proxy validity limit (commonly 11 months from execution). Proxies marked for a specific issue ("directed proxies") vote only on that issue.

Board removal requires a SPECIAL meeting called for that purpose. Under § 18.4, board removal cannot be added as a surprise item to a regular meeting agenda. The meeting must be called for the specific purpose, with notice identifying the removal-vote item.

Worked example: regular unit-owner vote

100 unit owners. Declaration silent on quorum (20% statutory floor applies). 15 in person, 10 by proxy. Vote: regular. 18 yes, 7 no.

• Total attendance: 25. Quorum: 20 (20% of 100). QUORUM MET.
• Vote type: regular. Threshold: majority of those present. Votes required: 51% of 25 = 13 yes votes.
• 18 yes votes meets the 13-vote threshold. PASSED.

Worked example: declaration amendment — the total-ownership trap

100 unit owners. 15 in person, 10 by proxy. Vote: declaration amendment. 18 yes, 7 no.

• Total attendance: 25. Quorum: 20. QUORUM MET.
• Vote type: declaration amendment. Threshold: 75% of TOTAL ownership = 75 yes votes required.
• 18 yes votes falls FAR short of the 75-vote threshold. FAILED — even though 72% of voters approved (18 of 25).

This is the trap. The same ballot tally that passes a regular vote (18 yes is 72% of voters) FAILS a declaration amendment (18 is only 18% of total). Boards must structure declaration-amendment campaigns to target 75 of 100 — meaning concerted outreach to non-voters is essential. Most Illinois condominium declaration-amendment attempts fail at this threshold.

Worked example: board removal — majority of those present

100 unit owners. Special meeting called under § 18.4 to remove the entire board. 40 in person, 20 by proxy. 35 yes, 25 no.

• Total attendance: 60. Quorum: 20. QUORUM MET.
• Vote type: board removal. Threshold: majority of those present = 51% of 60 = 31 yes votes.
• 35 yes votes meets the 31-vote threshold. PASSED — the board is removed.

Note the threshold-base contrast with declaration amendment: board removal is on those PRESENT (31 votes), whereas a declaration amendment is on TOTAL (75 votes). This is intentional — the legislature wants board removal to be procedurally accessible (the protection against captured boards) but declaration amendments to require broad consent (the protection of property rights).

Worked example: no quorum

100 unit owners. 8 in person, 5 by proxy. Vote: regular.

• Total attendance: 13. Quorum: 20. SHORT BY 7.
• Outcome: NO-QUORUM. The measure cannot proceed regardless of how the 13 attending vote.

The meeting chair should adjourn the meeting (or invoke reduced-quorum procedures if specified in the declaration for a reconvened meeting). Some Illinois condominium declarations permit a reduced quorum (typically 10%, but subject to the 20% statutory floor — so reduced-quorum provisions below 20% are unenforceable) at the SECOND attempt.

Worked example: declaration-specified higher quorum

100 unit owners. Declaration specifies 50% quorum. 35 in person, 10 by proxy. Vote: regular. 30 yes, 15 no.

• Total attendance: 45. Quorum: 50 (50% of 100). SHORT BY 5. NO-QUORUM.
• Outcome: NO-QUORUM. Even though 45% turnout would meet many associations' quorum, this declaration requires 50%.

The declaration-specified higher quorum controls (declarations can specify above the 20% floor, just not below). Boards considering whether to amend the declaration to reduce the quorum to 20% should weigh the procedural ease against the loss of broader-consent protection.

What this calculator does NOT model

The calculator implements the QUORUM-AND-SUPERMAJORITY math. It does NOT:

• Compute the § 18(a)(9) board / unit-owner meeting NOTICE timing — that is the work of the companion board-meeting notice calculator.
• Validate the form of proxies (signature, witness, delegation chain).
• Model weighted voting where votes are allocated by undivided-interest percentage or by unit type — the calculator treats each unit as one owner-equivalent.
• Model cumulative voting for board elections, if the declaration permits it.
• Validate compliance with the developer-control / transition provisions of § 18.2.
• Provide legal advice on whether a particular vote type is properly characterized as a declaration amendment, a bylaws amendment, or a regular vote.
• Model the § 27(b) developer-consent requirement for amendments that create rights or obligations of the developer.

For any consequential vote (declaration amendment, board removal, special assessment requiring owner ratification), retain Illinois counsel with condominium-election experience to oversee procedural compliance and the post-meeting documentation.

Counting conventions

The calculator rounds the effective quorum owner count UP to the nearest integer. A 20% quorum on 47 owners is 10 owner-equivalents (rounded up from 9.4), not 9. Illinois practice uniformly rounds up because partial owners do not exist.

The calculator counts each owner EXACTLY ONCE toward quorum. An owner who attends in person and has also submitted a proxy (later revoked by the in-person attendance) is counted only once. The calculator assumes the input counts are mutually exclusive — the meeting chair should not double-count.

For supermajority calculations on TOTAL OWNERSHIP (declaration amendment), the threshold is calculated EXACTLY (rounded up) on the total unit owners. For 100 owners at 75%, that is 75 yes votes (75.0 rounds to 75); for 99 owners at 75%, that is 75 yes votes (74.25 rounds up to 75).

For supermajority calculations on MAJORITY OF THOSE PRESENT (board removal, regular), the threshold is calculated on the greater of the quorum count and the actual attendance. This is a conservative interpretation; Illinois practice in some associations uses majority of votes actually cast, which produces a lower threshold.

Sources

Last reviewed: 2026-05-16 against:

• 765 ILCS 605/18 (bylaws contents, quorum, voting procedure).
• 765 ILCS 605/18(a)(8) (20% quorum statutory floor).
• 765 ILCS 605/18(a)(9) (board and unit-owner meeting notice requirements).
• 765 ILCS 605/18.4 (board powers, duties, and removal procedure).
• 765 ILCS 605/27 (declaration amendment — 75% of total ownership floor).
• 765 ILCS 605/27(b) (developer consent for amendments creating developer rights or obligations).
• 765 ILCS 605/18.2 (developer control transition — separate timing rules).
• CAI Illinois Chapter governance reference materials.