Domestic Content: How a Tax Bonus Turned Procurement Into a Financing Issue
Before 2022, a U.S. solar developer choosing between two otherwise bankable module or inverter suppliers could mostly frame the decision around price, performance, warranty, delivery and tariff exposure.
The Inflation Reduction Act changed that conversation.
Signed into law in August 2022, the IRA created a domestic-content incentive: use enough U.S.-made steel, iron and manufactured products, and the project can earn a larger federal tax credit. For an investment-credit project receiving the 30% rate, satisfying domestic content can add 10 percentage points. On a $250 million qualified investment, that is another $25 million of credit.
That is too large to leave with the tax-return team.
A tax investor now cares where a torque tube or cell was manufactured. A lender cares whether the tax-credit assumption survives a supplier substitution. Procurement needs rights to information it historically did not ask suppliers to provide. And the year in which construction begins can change the manufactured-products percentage the project has to hit.
The law created the incentive in 2022. It did not create the operating manual.
Treasury and the IRS published the first detailed framework in May 2023 through Notice 2023-38. That guidance split a project into two different tests — structural steel and iron on one side, manufactured products on the other — and then exposed a problem that had little to do with tax theory: the manufactured-products test could require direct-cost information that sits inside a supplier's books.
The next two years were largely about making that rule usable.
Notice 2024-41 created an elective safe harbor with assigned cost percentages. Notice 2025-08 rebuilt and expanded the tables for solar PV, land-based wind and battery energy storage. Final regulations under §§45Y and 48E then clarified something equally important for financing: under the new technology-neutral credits, the unit being tested is the individual qualified facility or energy storage technology, not whatever collection of assets the sponsor would prefer to treat as one project.
By 2026, domestic content is no longer a tax footnote. It is a procurement architecture, a diligence workstream and a model assumption with its own failure modes.
That history matters because each layer of guidance solved one problem while creating another.
ℹ️ Scope. This is a finance-oriented explanation of the federal domestic-content rules as of September 2026. Credit eligibility, beginning-of-construction rules, PFE/material-assistance restrictions and project-specific tax advice are separate analyses.
The first fork is the credit regime
Renewables professionals still say "the ITC" as though there is one investment credit. There is not.
Section 48 is the legacy Energy Investment Credit regime. Section 48E is the newer Clean Electricity Investment Credit for qualified facilities and energy storage technology placed in service after 2024. The production-credit counterparts are §45 and §45Y.
That distinction now changes the domestic-content threshold.
For ordinary non-offshore §48E projects, current law uses this manufactured-products schedule:
| Beginning of construction | §48E manufactured-products threshold |
|---|---|
| Before 16 June 2025 | 40% |
| 16 June–31 December 2025 | 45% |
| During 2026 | 50% |
| After 31 December 2026 | 55% |
Section 45Y follows its own statutory schedule: 40% for construction beginning before 2025, 45% in 2025, 50% in 2026 and 55% after 2026. Offshore wind has separate transitional percentages.
The legacy §48 and §45 rules generally use a 40% adjusted percentage for non-offshore projects.
That means a model input labelled only "Domestic Content Threshold = 50%" is incomplete. It should be downstream of at least three facts:
credit regime
+ beginning-of-construction date
+ project / technology classification
=
applicable domestic-content threshold
There is also a 2026 trap hidden in the timeline. Public Law 119-21 changed the underlying §45Y/§48E eligibility rules for applicable wind and solar facilities, and Notice 2025-42 addresses the new beginning-of-construction deadline. So the statement "a 2027 project has a 55% domestic-content threshold" is only a domestic-content statement. A wind or solar project must first establish that it still qualifies for the underlying credit at all.
Domestic content is an increase to a credit. It cannot rescue a project that has no underlying credit.
One project, two different tests
The phrase "domestic content percentage" makes the rule sound like one weighted-average calculation.
It is not.
The project is first split into two buckets:
- Steel or iron products that are primarily steel or iron and structural in function.
- Manufactured products and their manufactured-product components.
The two buckets fail differently.
| Steel / iron | Manufactured products | |
|---|---|---|
| Typical solar examples | steel module racking, steel piles or ground screws, foundation rebar | PV modules, inverters, PV trackers |
| Typical wind examples | tower and structural steel/iron items | wind turbine and its manufactured components |
| Typical BESS examples | structural reinforcing products | battery packs, containers/housings, inverters |
| Test | required manufacturing processes in the U.S. | domestic cost percentage ≥ applicable threshold |
| Failure mode | essentially binary by covered item | proportional |
Notice 2023-38 makes the classification step unusually important. If an item is a covered structural steel or iron product, the relevant manufacturing processes must occur in the United States, except for specified metallurgical processes involving refinement of steel additives.
But steel appearing somewhere in the project does not automatically put the item into that binary test.
The notice expressly lists nuts, bolts, screws, washers, cabinets, covers, shelves, clamps, fittings, sleeves, adapters, tie wire, spacers and door hinges as examples of items that are not structural steel or iron products for this purpose. A steel torque tube sitting inside a PV tracker can also be treated through the manufactured-product framework under the applicable safe-harbor table.
This is why the first diligence question is not "where was it made?"
It is "what is it under the rule?"
A classification error can make the rest of the calculation perfectly executed and still wrong.
The manufactured-products rule became a data-rights problem
The original 2023 framework sounds straightforward until someone tries to calculate it.
Under the actual-cost methodology, the domestic cost percentage is built from the manufacturer's direct costs — direct materials and direct labor under the §263A rules — rather than the purchase price paid by the project company.
The project owner can therefore know that it paid $40 million for modules and still not possess the number the tax calculation needs.
That creates a commercial asymmetry. The manufacturer has the cost data. The project owner has the tax benefit.
Those are not the same party.
Some suppliers may provide detailed cost information under confidentiality protections; others may provide certifications or limited data; others may resist disclosing information that reveals their cost structure or supply chain. The important financing point is not to assume one particular supplier behavior. It is to recognize that the data right has to exist before the project depends on it.
If the actual-cost route is going to matter, the supply agreement should address at least:
- what domestic-content information must be provided;
- in what form;
- whether an independent adviser can review underlying cost data;
- confidentiality and permitted disclosure to tax counsel, tax-credit investors, lenders and insurers;
- update obligations after a component substitution;
- liability or remedy for an inaccurate certification, where negotiated.
A tax assumption can therefore be won or lost in the equipment-supply agreement months before anyone prepares the tax return.
The safe harbor moved the bottleneck
Treasury and the IRS responded to the direct-cost problem in 2024.
Notice 2024-41 created an elective safe harbor that uses assigned cost percentages instead of requiring the taxpayer to reconstruct the manufacturer's actual direct-cost build-up for every listed item. Notice 2025-08 then issued the First Updated Elective Safe Harbor and updated the tables for:
- ground-mount solar PV;
- rooftop solar PV;
- land-based wind; and
- battery energy storage systems.
That did not eliminate diligence. It changed what diligence is about.
Under actual cost, the hard question is: can we get the supplier's cost data?
Under the elective safe harbor, the hard questions become: is this the right table, are the components classified correctly, are mixed-source items weighted correctly, and are we applying the table consistently?
Notice 2025-08 is explicit that where a taxpayer elects the updated safe harbor, the classifications and associated percentages have to be used as the notice requires. A project should therefore preserve not just a spreadsheet result but the exact notice, table and election methodology supporting it.
The IRS example shows why a generic weighted average is dangerous
Notice 2025-08 includes a 100 MWdc ground-mount tracker example.
In one version of the example, 60 MWdc of PV modules use domestic crystalline-silicon cells made with domestic wafers, and 80 MW of the tracker capacity is associated with domestic torque tubes. Using the notice's assigned percentages and nameplate-capacity weighting:
PV module contribution 44.0%
Torque-tube contribution 6.9%
Domestic Cost Percentage 50.9%
The project in the IRS example is a legacy §48 energy project, so its adjusted percentage is 40% and it passes.
The important lesson is not the 50.9%.
It is how the number was built.
The safe harbor is not a generic "domestic share × purchase price" calculation. Mixed-source items use the formula in the notice, generally tied to nameplate capacity or the capacity of the associated component. Production percentages have their own conditions. And the table changes depending on project configuration and, for solar, whether the project elects the domestic-cell-and-wafer columns.
If a §48E project beginning construction in 2026 independently calculated the same 50.9% domestic cost percentage under an applicable safe-harbor methodology, it would clear a 50% threshold by only 0.9 percentage points.
That is a very different diligence posture from "the project passes."
The 2025 final regulations changed the unit of account
The transition from §48 to §48E changed more than the threshold.
Under legacy §48, the domestic-content bonus can apply to an energy project, and the §48 regulations contain project-level aggregation concepts.
The final §§45Y/48E regulations do not import that flexibility.
For domestic content, more than one §45Y qualified facility cannot be combined into one facility to qualify, and more than one §48E qualified facility or energy storage technology cannot be combined into one unit to qualify. Each qualified facility or EST must satisfy the domestic-content requirement separately.
That matters on portfolios, campuses and co-located solar-plus-storage structures.
A sponsor may think commercially in terms of one project, one EPC, one interconnection agreement and one financing. The tax rule can still ask separate domestic-content questions for separate §48E qualified facilities and storage technology.
The model and diligence tracker should reflect the legal unit of account rather than the way the development team happens to name the site.
Interconnection creates a counterintuitive basis mismatch
Qualified interconnection property produces another result that is easy to miss in a model.
Under §48E, qualifying interconnection expenditures can be included in the qualified investment for certain lower-output facilities. But the final regulations state that qualified interconnection property is not part of the qualified facility for purposes of testing domestic content.
So the same interconnection property can be:
- outside the domestic-content test; yet
- inside the qualified investment to which the applicable credit percentage is applied, if the statutory interconnection-cost rules are satisfied.
That is not a contradiction. It is a consequence of the statute using one perimeter to define the property being tested and another set of rules to determine qualified investment.
For finance teams, the practical implication is important: do not build the domestic-content denominator simply by taking every line of tax-credit basis and asking whether it is domestic. The tax-basis schedule and the domestic-content component register are related schedules, not the same schedule.
By 2026, domestic content has a dangerous look-alike
Public Law 119-21 added separate restrictions involving prohibited foreign entities (PFEs) and material assistance for §§45Y and 48E.
Notice 2026-15 then created interim guidance for calculating the Clean Electricity Material Assistance Cost Ratio. That guidance reuses the 2023–2025 domestic-content safe-harbor tables in parts of the PFE analysis.
That reuse can create false familiarity.
Domestic content and PFE/material assistance are different tests serving different statutory purposes. A project can satisfy one and fail the other. The fact that the same table architecture appears in both analyses does not allow the two workstreams to be collapsed into one percentage.
In a 2026 model, keep them as separate switches:
Underlying credit eligible? YES / NO
Domestic-content bonus qualified? YES / NO
PFE / material-assistance restriction met? YES / NO
That separation is especially important now because the PFE rules apply to new construction timing and sourcing questions that did not exist when the original domestic-content guidance was issued.
The evidence file starts in procurement
A defensible domestic-content position is not one final percentage cell. It is the evidence chain underneath it.
A useful file normally has four layers.
1. Component register
Map the bill of materials into the tax classifications: steel/iron product, manufactured product and manufactured-product component. Record supplier, manufacturer, relevant country information and the safe-harbor row or actual-cost methodology used.
2. Supplier evidence
Keep the certifications, manufacturer statements, mill documentation and other records supporting the factual claims being made. The tax rule requires the taxpayer to certify compliance; procurement-system labels are not a substitute for evidence.
3. Methodology and version control
Record whether the project uses actual cost, Notice 2024-41 or Notice 2025-08, which table/configuration applies, and why. If the project contains mixed-source items, preserve the weighting calculation.
4. Change control
A component substitution is not just an engineering or procurement event. It can change the tax result.
The change log should therefore identify substitutions, re-run the relevant domestic-content test and escalate any move that reduces the cushion over the threshold or changes a steel/iron classification.
This is easiest during construction, when the supplier and procurement team are still engaged. Reconstructing the chain after commissioning is a much weaker control.
Direct pay makes failure more than a lost bonus
For a taxable sponsor using the ordinary credit rules, failure to satisfy domestic content generally means losing the domestic-content bonus while preserving the underlying credit if the other requirements are met.
For certain applicable entities using elective pay under §6417, domestic content can also affect how much of the underlying credit is payable.
The statute contains elective-payment phaseouts, subject to domestic-content exceptions. Treasury and the IRS have also provided transition relief.
As of September 2026, the IRS states that under Notice 2024-84, if an applicable entity makes the required attestation and maintains the required records for applicable credit property that begins construction before the later of January 1, 2027 or the issuance of further guidance, Treasury and the IRS will treat the attestation as establishing that a domestic-content exception is met.
That is a time-sensitive rule.
A model for an elective-pay project should not hard-code the statutory phaseout without also checking whether current transition guidance or a statutory exception applies.
The model needs three layers, not one pass/fail cell
The cleanest way to model domestic content is to separate legal eligibility, compliance mechanics and economics.
Layer 1 — legal regime
Credit regime §48E
BOC year 2026
Ordinary / offshore Ordinary
Manufactured-products threshold 50%
PWA / alternative-rate status Satisfied
Domestic-content rate increase 10 percentage points
If this is wind or solar, the model should separately confirm underlying §45Y/§48E eligibility under the post-2025 rules. If the project begins construction after 2025, PFE/material-assistance compliance should also sit in a separate assumption block.
Layer 2 — the two domestic-content tests
For steel and iron, use a register rather than a weighted average:
Steel pile / ground screw U.S. manufacturing test met TRUE
Foundation rebar U.S. manufacturing test met TRUE
Steel module racking U.S. manufacturing test met TRUE
Steel_Iron_Test = AND(all covered steel/iron rows) = TRUE
Do not use an imported nut, bolt or washer as the item that mechanically fails this test. Notice 2023-38 treats those listed non-structural items differently.
For manufactured products, the model should reproduce the actual-cost methodology or the elected safe-harbor table — not a homemade purchasing-spend proxy.
A useful output block is:
Domestic Cost Percentage 50.9%
Applicable threshold 50.0%
Cushion 0.9%
Manufactured-products test PASS
Steel / iron test PASS
Overall Domestic Content Requirement PASS
The cushion deserves its own cell. A 50.9% result and a 70% result are both "PASS," but they do not carry the same substitution or diligence sensitivity.
Layer 3 — economics
Assume, illustratively:
Qualified investment $250,000,000
Applicable investment-credit rate 30%
Domestic-content increase 10%
Incremental nominal credit value $25,000,000
Then compare that value with the actual transaction costs of qualifying:
- domestic sourcing premium;
- incremental procurement and documentation cost;
- any schedule impact;
- tax-investor or lender haircut for an uncertain position;
- contingency for substitutions or unresolved classifications.
The decision is not simply "is domestic sourcing cheaper than $25 million?"
The decision is whether the risk-adjusted incremental value of the bonus exceeds the incremental cost and execution risk required to preserve it.
That is a financing decision, not a tax slogan.
What diligence looks like when the rule is treated seriously
By the time a lender, tax-credit investor or tax adviser reviews the position, the useful questions are concrete:
- Which credit regime applies, and what beginning-of-construction date drives the threshold?
- For wind or solar, has underlying post-2025 credit eligibility been established separately?
- What is the legal unit of account — §48 energy project, §45Y qualified facility, §48E qualified facility or EST?
- Which items were classified as steel/iron products, and why?
- Which actual-cost or elective safe-harbor methodology was used?
- If Notice 2025-08 is used, which exact table and configuration applies?
- How were mixed-source components weighted?
- What is the percentage cushion over the threshold?
- What happens if a module, tracker, cell, wafer, inverter or structural item is substituted?
- Does the supply contract require the evidence the tax position needs?
- Is qualified interconnection property being kept outside the domestic-content test even where eligible interconnection costs enter credit basis?
- Is the PFE/material-assistance analysis being run separately?
- What does the financing model do if the domestic-content bonus is unavailable?
Those questions are much closer to the real transaction than "does the project use American equipment?"
The tax return comes last
Domestic content began as an industrial-policy bonus. The first guidance turned it into two technical tests. The actual-cost method then exposed a supplier-data problem. Safe-harbor tables solved part of that problem but made classification, table selection and version control more important. The technology-neutral credits changed the unit of account. The 2025 legislation added a separate foreign-entity sourcing regime that now sits beside it.
The result in 2026 is a rule that reaches backward through the entire transaction.
A procurement team can create or destroy the tax position. A supply contract can determine whether the position is provable. A construction substitution can erase the cushion. A model can overstate value if it confuses credit basis with the domestic-content perimeter. And a portfolio can look compliant in aggregate while an individual §48E facility fails on its own.
By the time the return is filed, almost every economically important decision has already been made.
That is why the domestic-content workstream belongs in procurement and financing from the start — not in a tax checklist at COD.
Primary sources: IRS — Domestic Content Bonus Credit · IRS Notice 2023-38 · IRS Notice 2024-41 · IRS Notice 2025-08 · Final §§45Y/48E regulations — T.D. 10024 / IRB 2025-12 · IRS Notice 2025-42 · IRS Notice 2026-15 · 26 U.S.C. §48E