Pension Accounting: Defined Benefit Plans, PBO & Pension Expense Under ASC 715

Published: March 27, 2026

Article by Ryan O'Connell, CFA, FRM

Pension accounting is one of the most complex topics in financial reporting — and one of the most consequential for investors and analysts evaluating a company’s true financial position. Under ASC 715, employers sponsoring defined benefit pension plans must measure the projected benefit obligation, track plan assets, and recognize a multi-component pension expense, all of which depend on actuarial assumptions that can materially affect reported earnings, leverage ratios, and enterprise valuation. This guide covers everything you need to know about pension accounting under U.S. GAAP, from the projected benefit obligation to funded status reporting and the corridor approach.

What Is Pension Accounting?

Pension accounting refers to the employer’s recognition, measurement, and reporting of obligations and costs associated with employee pension plans. The complexity arises primarily from defined benefit (DB) plans, where the employer promises a specified retirement benefit and bears the investment risk, longevity risk, and salary risk needed to fund that promise.

The accounting for defined contribution (DC) plans — such as 401(k) plans — is straightforward: pension expense equals the employer’s contribution for the period. No complex liability measurement is required because the employee bears the investment risk. The remainder of this article focuses on DB plan accounting, which is where the real complexity lies.

Note that pension accounting (formally called net periodic pension cost) addresses the employer’s financial reporting obligations. For individual retirement planning and account types, see our guide on retirement planning accounts.

The Projected Benefit Obligation (PBO)

The projected benefit obligation is the actuarial present value of all pension benefits earned by employees to date, measured using projected future salary levels. FASB chose the PBO over alternative measures because it best reflects the employer’s going-concern obligation.

Three measures of pension obligations exist, each using a different scope and salary basis:

PBO is always greater than or equal to ABO because it incorporates expected salary growth. For flat-benefit plans (where benefits are not tied to salary), PBO and ABO are equal. The PBO changes each period due to:

• + Service cost — benefits newly earned by employees during the period
• + Interest cost — growth in PBO due to the passage of time (beginning PBO × discount rate)
• ± Actuarial gains/losses — changes in actuarial assumptions or experience adjustments
• + Prior service cost — retroactive benefit increases from plan amendments
• − Benefits paid — payments to retirees reduce the obligation

Plan Assets and Funded Status

Plan assets are the investments held in a pension trust that are segregated and restricted specifically for paying pension benefits. These assets typically include equities, fixed-income securities, real estate, and other investments managed by the plan’s trustees.

Plan assets change each period due to employer contributions, actual returns on investments, and benefits paid to retirees. A critical distinction in pension accounting is between the actual return on plan assets (what the investments actually earned) and the expected return (a long-term assumption used in the pension expense calculation).

When plan assets exceed the PBO, the plan is overfunded and the employer reports a noncurrent pension asset. When the PBO exceeds plan assets, the plan is underfunded and the employer reports a pension liability — classified as current only to the extent that benefits expected to be paid in the next 12 months exceed the fair value of plan assets available for those payments, with the remainder as noncurrent. Aggregate funded ratios for large U.S. corporate pension plans have varied widely over time — dipping below 80% after the 2008 financial crisis and recovering above 100% in years when discount rates rose and equity markets performed well.

The Five Components of Pension Expense

Pension expense (formally, net periodic pension cost) consists of five components. Understanding each component and how it flows through the financial statements is essential for interpreting pension disclosures.

1. Service Cost — The actuarial present value of benefits earned by employees during the current period. Uses the benefits/years-of-service method with projected future salaries. Always increases pension expense. Under ASU 2017-07, service cost is the only component presented with compensation costs in operating income.
2. Interest Cost — The increase in PBO due to the passage of time, calculated as beginning PBO × the discount rate (settlement rate based on high-quality corporate bond yields). Always increases pension expense.
3. Expected Return on Plan Assets — The expected (not actual) return on plan assets for the period. This component reduces pension expense. The difference between actual and expected return is deferred as a gain or loss in accumulated other comprehensive income (AOCI).
4. Amortization of Prior Service Cost (PSC) — When a plan amendment grants retroactive benefit increases, the resulting PSC is recognized in other comprehensive income (OCI) and then amortized to pension expense over the remaining service years of affected employees. Generally increases pension expense.
5. Amortization of Net Gain/Loss — Cumulative actuarial gains and losses that exceed the corridor threshold are amortized into pension expense. The corridor approach (discussed below) determines when amortization is required.

Pension Expense Example

To illustrate how all five components come together, consider a realistic scenario for a large manufacturer with a defined benefit plan.

The Corridor Approach

Actuarial gains and losses arise from changes in assumptions (discount rate, salary growth, mortality) and from differences between expected and actual returns on plan assets. Rather than recognizing these volatile items immediately in pension expense, GAAP allows them to accumulate in AOCI and requires amortization only when the cumulative balance exceeds a threshold called the corridor.

The corridor equals 10% of the greater of the beginning PBO or the market-related value of plan assets (often simplified to fair value of plan assets in practice). Only the cumulative net gain or loss that exceeds this corridor must be amortized, and the minimum amortization is the excess divided by the average remaining service life of active employees.

Pension Accounting in OCI and AOCI

Two types of items related to pension accounting flow through other comprehensive income (OCI) and accumulate in accumulated other comprehensive income (AOCI) on the balance sheet:

1. Prior Service Cost (PSC) — When a plan is amended to grant retroactive benefit increases, the entire PSC is recognized immediately in OCI. It is then reclassified (amortized) from AOCI into pension expense over the remaining service years of the employees expected to benefit from the amendment.

2. Net Gain or Loss — Actuarial gains and losses (from assumption changes and actual-vs-expected return differences) are initially recognized in OCI. They accumulate in AOCI and are amortized into pension expense only when the cumulative balance exceeds the corridor threshold.

When amortization occurs, the reclassification entry moves the amount from AOCI into pension expense — reducing the AOCI balance and increasing (or decreasing, in the case of gains) reported pension expense for the period. These AOCI pension items also create deferred tax effects that must be tracked separately.

ASC 715 Reporting and Disclosures

ASC 715 requires comprehensive reporting of pension plan information across multiple financial statements:

Balance Sheet: The net funded status (plan assets minus PBO) is reported on the face of the balance sheet. An overfunded plan is reported as a noncurrent asset. An underfunded plan is reported as a liability — current to the extent benefits payable in the next 12 months exceed plan assets available for those payments, with the remainder noncurrent. Related AOCI balances (unrecognized PSC and net gain/loss) are reported in the equity section.

Income Statement: Under ASU 2017-07, service cost is presented with other compensation costs in operating income. All other components of net periodic pension cost (interest cost, expected return, amortization of PSC, and amortization of net gain/loss) are presented separately, typically below operating income.

Statement of Comprehensive Income: Changes in AOCI pension items — new PSC from plan amendments and actuarial gains/losses — are reported in OCI. Reclassification adjustments (amortizations from AOCI to pension expense) are also disclosed.

Note Disclosures: ASC 715 requires extensive disclosures including:

• Reconciliation of beginning and ending PBO
• Reconciliation of beginning and ending plan assets
• Components of net periodic pension cost
• Actuarial assumptions used (discount rate, expected return, salary growth rate)
• Plan asset allocation by category
• Expected future benefit payments for the next five years and beyond
• Expected employer contributions for the coming year

Other Postretirement Benefits (OPEB)

In addition to pensions, many employers provide other postretirement benefits (OPEB) — primarily retiree healthcare and life insurance — accounted for under ASC 715-60. The accounting framework is conceptually similar to pension accounting but has several important differences.

OPEB uses two key measures analogous to pension obligations:

• EPBO (Expected Postretirement Benefit Obligation) — the total present value of all expected future postretirement benefits
• APBO (Accumulated Postretirement Benefit Obligation) — the portion of the EPBO attributed to employee service to date, analogous to the PBO in pension accounting

Key differences from pension accounting include: OPEB plans are often unfunded (no segregated trust assets), benefits are based on healthcare costs rather than salary levels, and the attribution period for allocating benefits to service years may differ. Many large employers carry significant unfunded OPEB liabilities — General Motors, for example, has historically reported tens of billions in combined pension and postretirement benefit obligations.

For the present value mathematics underlying PBO and APBO calculations, see our guide on annuities and perpetuities.

Defined Benefit vs. Defined Contribution Plans

The shift from DB to DC plans has been one of the most significant trends in employee benefits over the past four decades. DB plans typically cost employers 5–6% of payroll, compared to approximately 3% for DC plans. The accounting complexity and financial risk of DB plans have been major drivers of this transition. Pension expense also affects earnings per share — for more on how complex items flow through the income statement, see our guide on dilutive securities and EPS.

Common Mistakes

Pension accounting involves numerous interrelated components. Here are the most frequent errors students and practitioners make:

1. Using actual return instead of expected return in pension expense. GAAP requires the expected return on plan assets in the pension expense formula. The actual return appears in the computation, but only the expected return reduces pension expense — the difference is deferred to AOCI.

2. Confusing PBO with ABO. PBO uses projected future salaries; ABO uses current salaries. GAAP requires PBO for funded status reporting. The two are equal only for flat-benefit plans where benefits are not linked to salary levels.

3. Forgetting that expected return reduces pension expense. The expected return on plan assets is subtracted in the pension expense formula — it is the only component that decreases expense. All other components either increase expense or can go either direction (net gain/loss amortization).

4. Confusing employer contributions with pension expense. The cash contribution to the pension trust is not the same as pension expense. Pension expense is determined by the five-component formula; contributions are a funding decision. The difference between expense and contributions affects the net pension liability or asset on the balance sheet.

5. Misapplying the corridor approach. Amortization of net gains/losses is required only when the cumulative balance in AOCI exceeds 10% of the greater of beginning PBO or market-related value of plan assets. Gains and losses within the corridor are not amortized.

6. Confusing service cost with interest cost. Service cost represents new benefits earned by employees during the current period. Interest cost is the time-value increase on the existing PBO — it reflects the unwinding of the discount on benefits already earned, not new benefits.

Limitations of Pension Accounting

1. Discount Rate Sensitivity — The settlement rate used to discount the PBO has an outsized impact. A 1% change in the discount rate can shift the PBO by 10–15% for a mature plan, dramatically altering funded status and pension expense.

2. Expected Return Assumption — Companies have discretion in setting the expected return on plan assets. An optimistic assumption reduces reported pension expense but does not change the actual economic cost. Analysts should compare the assumed rate to realized returns over time.

3. Salary Growth and Mortality Assumptions — PBO depends on projected salary increases and the expected duration of benefit payments. Longer lifespans and higher-than-expected salary growth increase the obligation.

4. Income Smoothing via AOCI — The corridor approach and AOCI deferral mechanisms delay the recognition of economic gains and losses. While this reduces income volatility, it can obscure the true economic position of the pension plan.

5. Disclosure Complexity — The extensive note disclosures required by ASC 715 provide valuable information but can be difficult for non-specialists to interpret, making cross-company comparison challenging even with complete disclosures.