A CPA's Guide to Commercial Solar Tax Treatment: What You Need to Know Before Advising Clients in 2026

Commercial solar has become a material tax planning opportunity for a wide range of business clients — and one that carries enough complexity in its interactions between the Investment Tax Credit, bonus depreciation, basis adjustment rules, at-risk limitations, passive activity considerations, and the transferability market that CPAs advising on it benefit from a current, comprehensive reference.

This article is written for CPAs, tax advisors, and CFOs with tax planning responsibility who are evaluating commercial solar for business clients. It covers the mechanics of the primary incentive provisions, the interactions between them, the financing structure implications that affect tax treatment, the transferability market as a planning tool, and the compliance documentation that should be in place before an ITC claim is filed.

The Primary Tax Incentive Provisions: A Technical Summary

Section 48 Investment Tax Credit (ITC)

The commercial solar ITC is governed by Section 48 of the Internal Revenue Code, as amended by the Inflation Reduction Act and subsequently modified by the One Big Beautiful Bill Act.

Base credit rate: 30% of the “energy percentage” of the qualified energy property’s eligible basis. For qualifying solar energy property placed in service under current law, the energy percentage is 30%.

Bonus adders: The IRA established stackable bonus credit adders that increase the total ITC rate above 30%:

Domestic Content Bonus: +10% (requires qualifying U.S.-manufactured steel, iron, and manufactured products)
Energy Community Bonus: +10% (for projects in designated Energy Community areas)
Low-Income Community Adders: +10% or +20% (for projects meeting qualifying criteria, subject to annual allocation)

Eligible basis: The eligible basis for the ITC is the cost of the qualifying energy property, reduced by any grants, tax-exempt bond financing, or subsidized energy financing received. For REAP grant recipients, the grant amount reduces the eligible basis for the ITC. For projects receiving Section 6418 transferability proceeds, the transfer itself does not reduce eligible basis — the credit is calculated on the full eligible basis before the transfer occurs.

Basis reduction for depreciation: This is the most commonly misunderstood interaction in commercial solar tax planning. When the ITC is claimed, the depreciable basis of the qualifying energy property must be reduced by 50% of the credit amount under Section 50(c). This rule applies regardless of whether the full credit is claimed in the current year or carried forward.

For a $1,000,000 solar installation claiming a 30% ITC of $300,000:

Depreciable basis = $1,000,000 − (50% × $300,000) = $850,000
Bonus depreciation is calculated on the $850,000 adjusted basis, not the $1,000,000 gross cost

Practitioners who calculate bonus depreciation on the full $1,000,000 without applying the Section 50(c) basis reduction are overstating the depreciation deduction. This error is material and creates an IRS examination risk.

Credit carryforward and carryback: The ITC may be carried back one year and carried forward 20 years if the taxpayer’s current-year regular tax liability is insufficient to absorb the full credit. The credit is subject to the limitation under Section 38(c) — it cannot reduce regular tax liability below the tentative minimum tax in AMT years, though this limitation has been significantly reduced in practical significance by TCJA AMT reforms for corporations.

Passive activity and at-risk limitations: For individuals and pass-through entities (partnerships, S corporations), the ITC is subject to the passive activity credit rules under Section 469. If the solar activity is a passive activity to the investor, the credit is suspended and can only be used against passive income. The at-risk rules under Section 465 also apply — credits (and losses) are limited to the amount the investor has at risk in the activity. Recourse and non-recourse financing are treated differently for at-risk purposes, with non-recourse financing generally not counted as at-risk unless it meets qualified non-recourse financing requirements.

Section 168 Bonus Depreciation

Current status: Under the One Big Beautiful Bill Act, 100% bonus depreciation has been restored and made permanent for qualifying property. This is the operative provision for commercial solar assets placed in service in 2026 and beyond.

Property classification: Commercial solar installations are classified as 5-year MACRS property under Asset Class 49.21 (Electric Utility Hydraulic Production Plant). The 5-year MACRS classification is the correct classification for both the panels and the associated inverters, racking, and electrical balance-of-system components.

Bonus depreciation election mechanics: Bonus depreciation under Section 168(k) is available automatically for qualifying property unless the taxpayer elects out. The election to opt out of bonus depreciation (for taxpayers where the deduction is not beneficial — for example, those in a net operating loss position) must be made on a timely filed return including extensions, on a class-by-class basis. A taxpayer who elects out of bonus depreciation for 5-year property elects out for all 5-year property placed in service during that year, not just solar.

Section 179 interaction: Section 179 expensing is available for qualifying solar property as an alternative to or in combination with bonus depreciation. For most commercial clients, bonus depreciation is preferable because Section 179 has a dollar limitation ($1,220,000 in 2026, subject to phase-out for total property placed in service above $3,050,000) that limits its availability for large systems. The interaction between Section 179 and bonus depreciation requires specific planning for clients near the phase-out thresholds.

Passive loss rules for individuals: The depreciation deduction generated by bonus depreciation on solar property is subject to the passive loss rules if the solar activity is passive to the investor. The deduction is suspended and can only offset passive income. This is a significant consideration for high-income individuals evaluating direct solar ownership in passive investment structures.

The Interaction Between ITC and Bonus Depreciation: A Complete Calculation

For a client evaluating the combined effect of the ITC and bonus depreciation on a commercial solar investment, the following walkthrough illustrates the complete Year 1 tax benefit calculation:

Facts:

Gross system cost: $1,500,000
ITC rate: 40% (30% base + 10% Domestic Content bonus)
Bonus depreciation: 100%
Client’s effective combined federal and state tax rate: 37%
Client has sufficient tax liability to absorb full benefits

Step 1: Calculate the ITC $1,500,000 × 40% = $600,000 ITC

Step 2: Apply the Section 50(c) basis reduction 50% × $600,000 = $300,000 basis reduction Depreciable basis = $1,500,000 − $300,000 = $1,200,000

Step 3: Calculate bonus depreciation $1,200,000 × 100% = $1,200,000 depreciation deduction Tax savings from deduction = $1,200,000 × 37% = $444,000

Step 4: Total Year 1 federal tax benefit $600,000 ITC + $444,000 depreciation tax savings = $1,044,000

Step 5: Net after-tax project cost $1,500,000 − $1,044,000 = $456,000

The effective net cost to the client, after Year 1 federal tax benefits, is $456,000 on a $1,500,000 gross investment — before any state incentives, REAP grants, or ongoing utility savings are applied.

For clients with state income tax at meaningful rates, the state depreciation deduction (which typically conforms to federal treatment, with some state-specific variations) adds further tax benefit. Several states have decoupled from federal bonus depreciation and require the standard MACRS schedule — confirm applicable state treatment before including state depreciation benefits in the financial model.

Financing Structure and Its Tax Treatment Implications

The financing structure of a commercial solar installation determines who claims the ITC and depreciation — and therefore which structure is optimal depends heavily on the client’s tax position.

Direct Ownership with Cash or Recourse Loan

The simplest structure: the business client directly purchases the solar system (with cash or with a recourse loan) and claims the ITC and bonus depreciation directly on its return.

Tax treatment: The full ITC and bonus depreciation are claimed by the client-owner. The recourse loan does not affect ITC eligibility. Loan interest is deductible under Section 163, subject to the business interest expense limitation under Section 163(j) for larger taxpayers.

Optimal for: Clients with substantial tax liability who can absorb the ITC and full bonus depreciation in Year 1. Clients with C-corporation structure where passive activity limitations are not an issue.

Non-Recourse Project Finance

The business client owns the solar system but finances it with non-recourse debt secured by the project assets.

Tax treatment: ITC eligibility is not affected by non-recourse financing per se. However, the at-risk rules under Section 465 limit the ability of individuals and pass-through entity investors to claim losses to the amount they have at risk — non-recourse financing generally does not count as at-risk unless it is qualified non-recourse financing (financing secured by the property from a qualified lender on commercially reasonable terms). For pass-through structures, the at-risk analysis is required before modeling the full depreciation benefit.

Power Purchase Agreement (PPA) — Client as Off-Taker

Under a PPA, the solar developer owns the system and sells power to the client at a contracted rate. The developer claims the ITC and depreciation; the client does not.

Tax treatment for client: PPA payments are operating expenses, fully deductible under Section 162 as ordinary business expenses. No capital asset on the client’s balance sheet. No ITC or depreciation benefit. The client captures economic benefit through below-market energy cost, not through tax incentives.

When PPA makes sense: Clients with insufficient tax liability to absorb the ITC and bonus depreciation directly (small businesses, nonprofits, government entities), clients with passive activity limitations that would suspend the credits and depreciation, or clients with balance sheet constraints that prefer off-balance-sheet energy financing.

Tax Credit Transfer (Section 6418)

The client installs and owns the solar system, claims the ITC, and sells (transfers) the ITC to a third-party credit buyer at a negotiated price (typically $0.88–$0.96 per dollar of credit).

Tax treatment for credit seller: The proceeds from the ITC transfer are taxable income to the seller — not as capital gain, but as ordinary income in the year received. The ITC itself is still generated and transferred on the seller’s return; the seller includes the transfer proceeds in income and may not “net” the proceeds against the credit basis. The basis reduction under Section 50(c) applies based on the full credit amount, not the transfer proceeds.

Tax treatment for credit buyer: The purchased ITC is applied against the buyer’s tax liability dollar-for-dollar. The credit has a transfer price basis equal to the amount paid, which affects the buyer’s tax position if the credit is subsequently disallowed — the buyer can deduct the transfer price paid as a loss in the year of disallowance. Tax credit insurance policies are available and recommended to protect against disallowance risk.

Critical compliance point for transfer transactions: The IRS requires both the transferor and transferee to file Form 3468 (Investment Credit), and specific notification requirements must be met. The transfer agreement must be in place and the relevant information exchange between parties must occur in the applicable tax year. Failure to comply with notification requirements can result in disallowance of the transfer.

Recapture Risk and the Five-Year Recapture Period

The ITC is subject to recapture under Section 50(a) if the qualifying property is disposed of or ceases to be qualifying property within five years of being placed in service. The recapture amount decreases by 20% for each full year the property remains in service:

Year of Disposition	Recapture Percentage
Year 1	100% of credit claimed
Year 2	80%
Year 3	60%
Year 4	40%
Year 5	20%
Year 6+	0% (no recapture)

Events that can trigger recapture:

Sale or transfer of the solar property to a non-qualifying purchaser
Casualty loss or destruction of the property
Change in use that causes the property to no longer qualify as energy property
For transferred credits, certain events at the project level

Implications for clients with transfer transactions: Recapture at the transferor level triggers a tax obligation on the transferor’s return, not the transferee’s. The transferee’s credit exposure is separate — if the underlying credit is disallowed (rather than recaptured), the transferee has recourse against the disallowance through the deduction mechanism described above.

Tax insurance: As discussed in the buyer’s guide articles of this series, tax credit insurance is available from specialty insurers to protect against recapture and disallowance risk. For clients who have transferred credits or received credits through transfer, insurance is strongly recommended. Premiums are typically 1–3% of insured credit value.

Documentation Checklist for ITC Claims

Proper documentation is essential for defending ITC claims on examination. The following checklist covers the primary documentation requirements:

Placed-in-service documentation:

Certificate of occupancy, building inspection sign-off, or utility permission to operate
Evidence of commercial operation (first generation data)
EPC contract and completion certificate

Property qualification:

Engineering documentation confirming the installation qualifies as solar energy property under Section 48
Equipment specifications for panels, inverters, and battery storage (if applicable)
Confirmation that the property is new qualifying property (not used property, subject to specific exceptions)

Eligible basis documentation:

Itemized project cost summary
Contractor invoices and payment records
Identification and exclusion of any non-qualifying costs from the eligible basis calculation
Documentation of any grants or subsidized financing received (REAP, state grants) and their treatment in the eligible basis reduction

Domestic Content qualification (if claiming bonus):

Manufacturer certifications for U.S.-manufactured content percentages for panels, inverters, and racking
Supply chain documentation as required by IRS guidance
Calculation of manufactured products adjusted cost basis meeting the qualifying threshold

Energy Community qualification (if claiming bonus):

IRS Energy Community mapping tool documentation confirming project location qualifies
Print or download of applicable Energy Community designation with project address

Transfer documentation (if applicable):

Section 6418 transfer agreement
Evidence of notification to IRS as required by regulations
Form 3468 filed by both transferor and transferee

Safe harbor documentation (if applicable):

Evidence of qualified costs incurred meeting the 5% threshold in the safe harbor year
Continuous construction documentation through commissioning

Common Planning Errors to Avoid

Failing to apply the Section 50(c) basis reduction. The most prevalent computational error in commercial solar tax work. The depreciable basis must be reduced by 50% of the credit amount before calculating bonus depreciation. Overlooking this produces an overstated depreciation deduction and an understated ITC — a combination that will not survive examination.

Treating transfer proceeds as capital gain. Section 6418 transfer proceeds are ordinary income, not capital gain, regardless of the holding period of the underlying credit.

Claiming bonus depreciation on the full project cost when a REAP grant was received. The REAP grant reduces eligible basis, which reduces both the ITC and the depreciable basis. Modeling bonus depreciation on the pre-grant project cost overstates the deduction.

Not confirming at-risk and passive activity status for pass-through clients. For individual taxpayers and pass-through entities, the ITC and depreciation benefits are subject to at-risk and passive activity limitations that can significantly alter the timing and availability of the tax benefits. Confirm the client’s activity-level involvement and financing structure before modeling full Year 1 benefit utilization.

Missing the election to opt out of bonus depreciation when appropriate. For clients in NOL positions, clients with existing NOL carryforwards that will expire, or clients subject to certain state tax regulations that do not conform to federal bonus depreciation, the optimal tax treatment may be to elect out of bonus depreciation and use the standard MACRS schedule instead. The election must be made on a timely filed return.

Frequently Asked Questions From Tax Professionals

For a client who is both the ITC claimant and the credit transferor, in what order do the computations occur? The ITC is first calculated on the eligible basis (reduced by grants and other required adjustments). The basis reduction under Section 50(c) is applied to reduce the depreciable basis. The bonus depreciation is then calculated on the reduced basis. The transfer of the credit occurs after these computations — it does not affect the basis reduction calculation. The transfer proceeds are recognized as ordinary income in the same taxable year in which the transfer agreement is executed and the credit would have been first allowed.

Can a taxpayer claim both the Section 48 ITC and the Section 30C Alternative Fuel Vehicle Refueling Property Credit on the same solar carport that also includes EV charging? The two credits apply to distinct property. Section 48 applies to the solar generation components (panels, inverters, racking). Section 30C applies to the EV charging equipment. If the solar carport project includes both solar generation and EV charging equipment, both credits may be claimed on the respective qualifying property, provided location and other qualification requirements for each credit are independently met. The eligible basis for each credit must be separately calculated and documented.

How is the Section 50(c) basis reduction applied when multiple bonus adders are stacked? The basis reduction under Section 50(c) is 50% of the total credit claimed — regardless of whether that credit consists of only the base 30% rate or includes additional adders. If the total ITC rate is 50% (30% base + 10% Domestic Content + 10% Energy Community), the basis reduction is 50% × (50% of eligible basis), which equals 25% of eligible basis. On a $1,000,000 project with a 50% total ITC: credit = $500,000; basis reduction = $250,000; depreciable basis = $750,000.

For a client using a sale-leaseback structure to monetize the ITC, what are the key qualification concerns? Sale-leaseback transactions involving solar energy property must meet specific requirements under Section 168(h) and Section 50 to preserve ITC and depreciation benefits. The lessee in a true lease (the original solar developer or owner) is treated as the owner for tax purposes and claims the credit, while leasing the property back to the original installer or user. The structure requires careful attention to the “true lease” versus “conditional sale” distinction, the “at-risk” rules for the lessee, and the anti-churning rules that could affect bonus depreciation availability. This is specialized tax equity structuring work that requires coordination with tax equity counsel.

Commercial solar is a legitimate and material tax planning opportunity for business clients across a wide range of industries and sizes. The ITC and bonus depreciation combination creates a Year 1 tax benefit profile that is exceptional by any comparison, and the transferability market has made these benefits accessible to clients regardless of their ability to directly absorb the credits. The technical complexity of the provisions rewards careful analysis and proper documentation — outcomes that benefit the client and that reflect well on the advisors who guide them.