Other employer-benefits deadlines · Required at all times — adopt by plan effective date

Section 125 cafeteria plan — the written-document requirement

A Section 125 cafeteria plan is the legal vehicle that allows employees to pay for benefits with pre-tax dollars. To qualify under §125, the plan must have a written document in place — adopted, signed, and effective. Without one, the plan isn't a §125 plan, and pre-tax contributions can be retroactively reclassified.

The written-document requirement

IRC §125 and Treas. Reg. §1.125-1 require a Section 125 cafeteria plan to be in writing. The document must be adopted by the employer, signed by an authorized representative, and effective before the plan year it applies to. Operating without a written document — or operating with a document that doesn't cover the required content categories — disqualifies the plan from §125 tax treatment.

The consequence isn't a small civil penalty. Pre-tax contributions made to a disqualified plan are retroactively reclassified as taxable wages, with the corresponding income-tax and FICA reconciliation due. For an employer with 200 employees averaging $4,000/year of Section 125 elections, a single-year disqualification can mean six-figure payroll-tax adjustment exposure.

What the document must cover

Under Treas. Reg. §1.125-1, the written document must include specific content categories:

A specific description of each elective benefit offered (health, dental, vision, FSA, HSA contributions, dependent care, etc.).
Eligibility rules for participation.
Election procedures, including the rule that elections are irrevocable for the plan year except for limited mid-year change events.
Manner of contribution / compensation-reduction mechanic.
Maximum amount of elective contributions (by category).
Plan year, with start and end dates.
FSA-specific rules if FSAs are offered (use-it-or-lose-it, grace period, or carryover; uniform-coverage rule for health FSAs; reimbursement procedures).
Adoption and effective date.

Section 125 written-document checklist

Required content categories per Treas. Reg. §1.125-1.

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Specific description of each elective benefit offered
Each qualified benefit a participant can elect is named: health, dental, vision, FSA, HSA contributions, dependent care, etc.
Eligibility rules for participation
Who is eligible (full-time, hours threshold, waiting period) and any classifications excluded from participation.
Election procedures including timing rules
How and when participants make elections, the irrevocable-election rule for the plan year, and the limited circumstances under which mid-year changes are allowed.
Manner of contribution / compensation-reduction mechanic
How participant elections reduce taxable compensation. Salary-reduction agreements, employer contributions (flex credits), and any after-tax contribution mechanism.
Maximum amount of elective contributions
Maximum dollar amount of pre-tax salary reduction available under the plan, by benefit category.
Plan year defined
12-month plan year (or short plan year for a new plan), with the start and end dates explicitly stated.
If FSAs offered: required FSA rules incorporated
Use-it-or-lose-it rule (or grace period or carryover provision), uniform-coverage rule for health FSAs, and reimbursement procedures.
Adoption + effective date documented
Plan document is signed and dated by an authorized employer representative, in advance of the plan effective date.

Self-assessment for orientation only. A real §125 plan document is drafted by ERISA / employee-benefits counsel and signed before the plan effective date. Operating without a written document disqualifies pre-tax contributions and exposes the sponsor to retroactive payroll-tax issues.

Worth noting

Adopt before the effective date — not after

The adoption rule is strict: the §125 plan document must be signed and adopted before the plan effective date. A document signed mid-year covering retroactive elections doesn't qualify for §125 treatment for periods before the adoption date.

The fix when this gets missed: adopt prospectively going forward, and treat the pre-adoption period as taxable. Trying to back-date a §125 plan document is a recurring source of payroll-tax remediation work — the IRS position is consistent that adoption must precede the period being covered.

When the document needs to be updated

The §125 plan document is a long-lived governing document, but it must be updated when material changes occur:

New benefits added (or removed) from the menu.
Eligibility rules changed.
Maximum-contribution amounts changed.
FSA carryover or grace-period election changed.
Plan year restated.

A typical mid-market plan refreshes the §125 document every 3–5 years, even when nothing material changes, just to incorporate recent IRS guidance and ensure the document reflects current operating reality.

What this guide doesn't do

This guide surfaces the existence and content of the §125 written-document requirement. It is not a §125 plan document. Drafting and maintaining one is the work of ERISA / employee- benefits counsel or a qualified vendor. If your plan doesn't have a current written §125 document, that's the conversation to have first — separate from any other compliance item on this site.

Sources

26 U.S.C. §125 — Cafeteria plans — The statute itself; cafeteria plans must be written and qualify under §125 for the tax treatment.
Treas. Reg. §1.125-1 — Cafeteria plans (proposed regulations) — Treasury proposed regulations interpreting §125, including required content of the written plan document.