The Material Assistance Cost Ratio: A Purity Test, Not a Domestic Content Test

The material assistance cost ratio reuses the tables, the component categories and much of the arithmetic from the domestic content adder. That resemblance is the problem. The two tests look alike, are computed alike, and ask different questions — one about how much of a project is American, the other about how much of it is not from a prohibited entity.

A module manufactured in Vietnam by an unrelated supplier helps your MACR and does nothing for domestic content. A module manufactured in Texas by a subsidiary of a specified foreign entity does the reverse. Same bill of materials, two ratios, and they can move in opposite directions.

This is the eighth post in the policy and regulation series and the last on FEOC. You will get the formula, why it is not a domestic content test, the threshold schedule by credit and year, the three safe harbours that make the calculation practicable, how far supplier certifications reach, and when the rules bite.

ℹ️ Note: This describes how these rules work in practice. It is not tax or legal advice. The guidance is interim, proposed regulations are forthcoming, and safe harbour tables remain to be published.

What Does MACR Actually Measure?

The share of direct costs that did not come from a prohibited foreign entity. Morgan Lewis gives the formula precisely:

MACR = (A − B) / A

A = Total Direct Costs of manufactured products or materials
B = PFE-sourced or PFE-produced Direct Costs

Baker Botts describes the same measure as "the percentage of total costs of a facility or product attributable to components produced by non-prohibited foreign entities," with a facility passing when its MACR meets or exceeds the statutory threshold.

Two features of that formula are worth pausing on.

It is a ratio of exclusion, not inclusion. You are not demonstrating that a share of the project came from approved sources. You are demonstrating that only a small enough share came from prohibited ones. Everything neutral — a supplier in Germany, Korea, Vietnam or Mexico with no PFE connection — sits in the numerator and helps you.

It uses direct costs. Like the domestic content calculation covered earlier in this series, the inputs are the manufacturer's direct material and labour costs rather than the price paid. The same commercial confidentiality problem applies, and it is the reason the safe harbours exist.

Why Is It Not a Domestic Content Test?

Because "American" and "not prohibited" are different sets, and a project can score very differently on each.

	Domestic content adder	Material assistance (MACR)
Question asked	How much is made in the USA?	How much is not from a PFE?
A Vietnamese supplier, unrelated to any PFE	Counts against you	Counts for you
A US plant owned by a specified foreign entity	May count for you	Counts against you
Consequence of failing	Lose a 10 percentage point adder	Lose the entire credit
Nature	Opportunity	Eligibility condition

The last row is the one that should govern how the two are prioritised. Domestic content is worth ten percentage points and a project that misses it still has a credit. Missing the MACR threshold disqualifies the credit entirely.

That asymmetry is frequently inverted in practice, because domestic content has been in the market longer, has a clearer commercial narrative, and is owned by a procurement team with a target. MACR arrived later, is owned by nobody in particular, and is the one that can zero the entire position.

What Are the Thresholds?

They vary by credit and rise over time. The schedule under Notice 2026-15:

Credit	2026	2027	2028	2029	2030+
Qualified facilities (45Y, 48E)	40%	45%	50%	50%	55%
Eligible components (45X)	50%	55%	55%	60%	60%
Energy storage (48E)	55%	escalating

Morgan Lewis confirms the two anchor figures: "electrical generation facilities claiming Tech Neutral Credits that begin construction in 2026 must have a MACR of at least 40%," and "solar energy components claiming the Manufacturing Credit that is sold during the 2026 calendar year must have a MACR of at least 50%."

Energy storage starts higher, at 55% for 2026, and escalates from there — the "more stringent material assistance standards" applied to storage that the previous post described. A storage project is therefore held to a threshold in 2026 that a generation facility does not reach until 2030.

One category runs the other way: Baker Botts notes that critical minerals currently carry a zero percent threshold, reflecting a supply chain where a meaningful non-PFE share is not presently achievable.

As with the domestic content adder, the applicable threshold attaches to the year construction begins — which adds a sixth consequence to the beginning-of-construction date, and one where, unusually, an earlier date is unambiguously better.

What Are the Three Safe Harbours?

Three mechanisms, each removing a different piece of the calculation's difficulty. Morgan Lewis sets them out.

The ID Safe Harbor uses the 2023–2025 safe harbour tables to "identify the applicable MPs, MPCs and Constituent Materials that must be tested." It answers the first question — what do I have to look at? — by borrowing the component taxonomy already built for domestic content.

The Cost % Safe Harbor allows reliance on "assigned cost percentages" from those tables "in lieu of measuring actual direct costs." This is the one that makes the exercise possible at all, for the same reason it matters in the domestic content context: actual direct costs belong to the manufacturer.

The Cert Safe Harbor permits use of a "supplier material assistance certification" to establish either PFE status or direct costs, in place of the general procedures.

Baker Botts describes the certification route with its important qualifier: taxpayers may rely on "certifications provided by suppliers (unless it knows or has reason to know the certification is false)."

That reason-to-know standard is doing substantial work. Reliance is not automatic — it is available to a taxpayer that does not have contrary information and has not wilfully avoided acquiring it. A sponsor holding a supplier certification alongside public reporting that contradicts it is not in a safe harbour.

How Far Up the Supply Chain Does Certification Reach?

Not clearly enough, and this is the most commercially significant open question in the regime.

Morgan Lewis identifies the ambiguity directly: it remains unclear "the extent to which, absent a certification of direct costs, a supplier must certify to PFE involvement further up the supply chain."

The practical shape of the problem is easy to state and hard to solve. A sponsor obtains a certification from its module supplier. That supplier is not a PFE. But its cell supplier may be, or its wafer supplier, or the entity that owns 30% of its polysilicon source. Does the certification have to reach those tiers, and if so how far?

Until that is settled, three things are worth doing.

Contract for the deepest certification available. A supply agreement that requires certification of the supplier's own status is weaker than one requiring certification as to sub-suppliers, and the difference costs nothing to negotiate at order stage.

Preserve the reason-to-know position. Document what was asked, what was provided, and what was reviewed. The safe harbour depends on the absence of contrary knowledge, which is a record rather than an assertion.

Expect to redo it. Treasury must publish PFE-specific safe harbour tables, and reliance on the interim approach runs only until shortly after those tables appear. A position taken now has a known expiry.

Which Suppliers Count as Prohibited?

The same entity tests from the previous post, applied one layer out. A supplier is a prohibited foreign entity on exactly the criteria that would disqualify the sponsor — specified foreign entity status, or foreign influence through ownership, debt, officer appointment rights or effective control.

That symmetry is easy to state and awkward to apply, because a sponsor screening its own cap table has access to its own records and a sponsor screening a supplier does not.

The thresholds are the same ones: a single specified foreign entity holding at least 25%, multiple holding 40%, at least 15% of debt, a right to appoint a covered officer. A supplier can therefore be a prohibited foreign entity while being incorporated in a friendly jurisdiction, operating a plant in one, and presenting as an ordinary commercial counterparty. Nationality of incorporation is not the test and never was.

Three consequences for how sourcing diligence should be run.

A country-of-manufacture list is not a MACR analysis. It answers the domestic content question. The MACR question is about the ownership and control of the manufacturer, which a bill of materials does not record.

Corporate structure changes matter mid-contract. A supplier that is clean at order stage can become foreign-influenced through an equity raise or a debt placement it never mentions. Where the supply relationship spans years, a one-time screen is a snapshot.

The tiers multiply the problem. Screening a module supplier is tractable. Screening its cell supplier, and that supplier's wafer source, is the question the certification regime exists to answer — and, as above, the depth required is not yet settled.

When Do the Rules Apply?

To projects starting after 2025, with interim reliance running until the forthcoming tables are published.

Morgan Lewis sets out the reliance periods. For qualified facilities and energy storage, the guidance applies to projects "construction of which begins after December 31, 2025, until 60 days after the publication of forthcoming safe harbour tables." For eligible components, it covers those "sold in tax years beginning after July 4, 2025, until the date that the forthcoming safe harbour tables are published."

Baker Botts records the same structure and a comment deadline of 30 March 2026.

The exemption for earlier starters is the single most valuable planning point in this post. Projects beginning construction before 1 January 2026 are generally outside the material assistance requirement altogether. For a project near that boundary, establishing beginning of construction is not merely a credit-vintage decision — it determines whether an entire eligibility test applies.

What Happens If the Threshold Is Missed?

The credit goes. Not a reduction, not a haircut proportional to the shortfall — missing the material assistance cost ratio threshold disqualifies the entire credit for the facility or component.

That cliff shape deserves emphasis because it is unusual among the rules in this series. Domestic content is proportional in its input and binary only at its threshold, and failing it costs a defined ten percentage points. Prevailing wage failures are curable through correction and penalty. Energy community either applies or does not, but its absence leaves the base credit intact.

MACR has no cure provision, no partial credit, and no fallback position. A project at 38% against a 40% threshold is in the same place as one at 5%.

Two planning consequences follow from an all-or-nothing test.

Margin is worth paying for. The difference between passing at 41% and passing at 60% is not merely comfort — it is the difference between a position that survives a supplier reclassification and one that does not. Where a component's PFE status is uncertain, the honest modelling treatment is to run the ratio both ways and look at whether the position holds in the adverse case.

Thin positions are expensive to insure. As covered in the diligence post earlier in this series, insurers underwrite tax positions on the strength of process and evidence. A MACR position with two percentage points of headroom and an unresolved question about a sub-supplier is exactly the profile that attracts a high premium or an exclusion.

How Is the Risk Allocated in Supply Contracts?

Badly, so far, and it is now a live commercial negotiation rather than a legal formality.

The mechanism available is supplier certification, and the market has moved to provide it. As the previous post noted, Morgan Lewis reports that manufacturers now certify "their non-PFE status to provide customers with comfort," with parties "working with third-party accounting and legal advisors to document their FEOC-compliant status."

Their assessment of the negotiation is worth quoting because it is unusually direct: contractual discussion "around the allocation of risk and certification... has been challenging."

The difficulty is that a certification is a representation about facts, and the consequence of it being wrong is catastrophic and entirely one-sided. A supplier that certifies incorrectly has misstated its ownership; the buyer loses its entire tax credit. No supplier wants to stand behind that exposure, and no buyer can accept a certification that comes with no recourse.

Three provisions are therefore worth fighting for at order stage, in descending order of value.

Certification with specified depth. Not merely "we are not a PFE" but a representation reaching sub-suppliers, or at minimum disclosure of which tiers the certification covers.

A continuing obligation to notify. Ownership and debt structures change. A certification given once, with no duty to update, protects only the day it was signed.

An indemnity sized to the credit, not to the contract. This is where negotiations stall, and predictably so — the loss is a multiple of the supply contract's value. Where a full indemnity is unobtainable, a price adjustment mechanism or a right to reject and re-source is worth more than nothing.

How Do You Model MACR in Excel?

On the same bill of materials as the domestic content calculation, as a second and independent ratio. Building them in one sheet is what exposes the divergence.

The inputs

Assumptions, labelled as such — use the tables applicable to your BOC year:

BOC year                              2026
MACR threshold (qualified facility)   40%
Domestic content threshold            50%
Total direct costs (A)                $180,000,000

The two ratios on one bill of materials

Component          Direct cost   PFE-sourced?   US-made?
PV modules          $54,000,000        No           No   (Vietnam, unrelated)
Inverters           $21,600,000        No          Yes
Trackers            $32,400,000        No          Yes
Cells in modules    $28,800,000       YES           No
Transformers        $10,800,000        No          Yes
Balance of system   $32,400,000        No          Yes

B (PFE direct costs)                            = $28,800,000
MACR = (180.0 − 28.8) / 180.0                   = 84.0%   vs 40% → PASSES

Domestic content (US-made share)                = 53.5%   vs 50% → PASSES (narrowly)

Where they diverge

Now change one line. Move module assembly from Vietnam to a US plant owned by a specified foreign entity:

Domestic content   rises   (US-made share increases)          → more comfortable
MACR               falls   (PFE-sourced direct costs rise)    → closer to failing

One procurement decision, two ratios, opposite directions. A sourcing strategy optimised for the domestic content adder can walk a project toward a MACR failure, and the domestic content team will report it as an improvement.

What each failure costs

Domestic content failure  → lose 10 percentage points          = $25,000,000
MACR failure              → lose the entire credit             = $75,000,000

Three times the exposure, on the test that gets less attention.

The monitoring the position needs

Supplier certifications        obtained, dated, and reviewed against public information
Reason-to-know record          what was asked, provided, checked
Table version                  interim guidance vs forthcoming PFE-specific tables
Re-test trigger                publication of the new tables (+60 days)

ℹ️ Note: Build MACR and domestic content in the same model on shared component rows, with separate flags for Is_PFE_Sourced and Is_US_Made. Keeping them in separate spreadsheets is how a project optimises one into a failure of the other.

To run the full version — both ratios on a single bill of materials, safe harbour percentages applied per the applicable tables, and certification status tracked by supplier — prompt Dezzmond with your component list and sourcing data.

What Do Lenders and Tax Equity Actually Check?

• Did construction begin before 1 January 2026? If so, material assistance may not apply at all.
• What is the MACR, and what is the margin over the threshold? Thin margins on an all-or-nothing test are expensive to insure.
• Which safe harbour is the calculation built on? ID, cost percentage, certification, or actual direct costs.
• Are supplier certifications in writing, dated, and from the right entity? And do they reach sub-suppliers.
• Is there anything that contradicts a certification? The reason-to-know standard is where reliance fails.
• Has the position been tested against both ratios? Domestic content and MACR on the same bill of materials.
• What is the plan when the PFE-specific tables are published? Reliance expires shortly afterwards.

Frequently Asked Questions

How is the material assistance cost ratio calculated?

As (A − B) / A, where A is total direct costs of manufactured products or materials and B is the direct costs sourced or produced by prohibited foreign entities. It measures the share that is not PFE-derived.

Is MACR the same as domestic content?

No. Domestic content measures the US-made share; MACR measures the non-prohibited share. A non-PFE supplier outside the United States helps MACR and not domestic content, and the two can move in opposite directions on the same procurement decision.

What threshold does my project need?

For qualified facilities beginning construction in 2026, at least 40%, rising in later years. Eligible components sold in 2026 need 50%. Energy storage starts higher at 55% for 2026 and escalates from there.

Can I rely on a supplier's certification?

Generally yes, under the certification safe harbour — but not where the taxpayer knows or has reason to know the certification is false. How far certification must reach up the supply chain is not yet settled.

Which projects are exempt?

Projects beginning construction before 1 January 2026 are generally outside the material assistance requirement, which makes the beginning-of-construction date decisive for anything near that boundary.

Closing: Series A, and the Date Underneath All of It

Eight posts on policy and regulation, and one date runs through every one of them.

Beginning of construction fixes credit eligibility under the OBBBA termination rules. It starts the four-calendar-year continuity clock, where 31 December and 1 January are a year apart. It sets the domestic content threshold on a schedule rising five points a year. It locks energy community status for the life of the credit. It determines whether the prevailing wage exemption applies. And it decides whether the material assistance test applies at all.

Six consequences, one date, and in normal practice six different people arguing for moving it in directions that conflict. The continuity clock wants January. Domestic content wants December. Material assistance wants December. Energy community wants whichever side of the list refresh is favourable. No single team sees all six, which is the strongest argument this series has made for holding them in one model rather than six memos.

The next series turns to tax structuring — the partnership flip, transferability, recapture and depreciation — where the question stops being whether a credit exists and becomes who is able to use it.

Sources: Morgan Lewis — Meeting the MACR: IRS Interim Guidance on the Material Assistance FEOC Limitation · Baker Botts — Treasury and IRS Guidance on Material Assistance by Foreign Entities of Concern · Bracewell — FEOC and Material Assistance Rules for Clean Energy Tax Credits