Dr. Abass Mohammed 
I. Executive Summary for Industry and Governance Practitioners
This paper applies a clause-level empirical methodology to Diminishing Musharakah, the dominant Islamic home financing structure in the United States, to test whether it functions as a genuine risk-sharing partnership or as a conventionally structured debt instrument operating under alternative terminology. The analysis identifies three findings that practitioners, Shari’ah boards, and regulators should treat as priorities:
Structural Convergence. Across the four institutions that originate the large majority of U.S. Diminishing Musharakah contracts, clause-level scoring on a validated sixvariable instrument produced composite scores of 23.70 to 36.65 out of 100 — uniformly within the “significant debt replication” category. The contractual language of partnership does not, on its own, indicate how risk is actually allocated at default.
A Governance Gap, Not a Governance Failure. Shari’ah board review is concentrated at contract origination and evaluates linguistic and sequential compliance rather than default-time performance. This “Compliance Substitution” allows formal approval to stand in for substantive risk-sharing without any single actor intending the outcome.
An Institutional, Not Individual, Cause. The convergence toward debt-like terms is best explained as Institutionalized Debt Convergence — a rational adaptation to Basel III capital adequacy rules, GSE secondary-market requirements, and UCC Article 9 enforcement norms, rather than a failure of individual institutional intent.
Practitioner Recommendation: Institutions and Shari’ah supervisory boards should incorporate the Shari’ah Substance Test (SST) into both product design and postorigination review, extend governance oversight to default and foreclosure behavior rather than origination language alone, and evaluate the Substantive Risk-Sharing Model (SRSM) proposed in Section VII as a design pathway toward contracts that are commercially viable and substantively compliant.
II. Abstract
Islamic home financing in the United States has historically been evaluated by its contractual form — whether a document uses the vocabulary of co-ownership rather thanthe vocabulary of a mortgage. This study asks a different question: does the underlying economic substance of these contracts match that form once they are tested against default handling, cost allocation, and judicial enforcement outcomes? Using a documentary legaleconomic methodology applied to the primary contracts, land registry filings, and federal and state court records of the four leading U.S. providers of Diminishing Musharakah, this paper finds a consistent and substantial gap between the promise of equity partnership and its contractual reality. We argue that this gap is structurally produced rather than incidental, and we propose both a diagnostic instrument and a design framework to close it.
III. Introduction:
The Formalism Problem The prohibition of riba (usury) in Islamic commercial jurisprudence has pushed American Islamic financial institutions to engineer alternatives to the conventional mortgage. The dominant alternative, Diminishing Musharakah, is framed as a joint-ownership partnership: the institution and the client jointly acquire the property, and the client progressively purchases the institution’s share while paying rent on the remaining portion. The central claim made to consumers and regulators alike is that this structure shares risk in a way a conventional mortgage does not. That claim has rarely been tested against what actually happens inside these contracts when a household falls behind on payments, when a property loses value, or when a dispute reaches a courtroom. Legal form and economic substance can diverge quietly, inside clauses that few consumers or even regulators read closely. This paper’s underlying dissertation research set out to measure that divergence directly, rather than assume it away in either direction.
IV. Methodology: Documentary Legal-Economic Synthesis
The analysis applies a documentary, multi-case legal-economic methodology to the four institutions that, according to Home Mortgage Disclosure Act origination data and Islamic Finance Council USA industry reporting, account for over 90% of documented Diminishing Musharakah and co-ownership residential originations in the United States:Guidance Residential, University Islamic Financial, Lariba/American Finance House, and Devon Bank.
4.1 Data Sources
Primary contractual instruments, county land registry filings, and federal and state court records spanning January 2007 to December 2025 were collected and coded using a structured documentary protocol, with inter-rater reliability procedures applied to the coding of contractual clauses.
4.2 The Shari’ah Substance Test (SST)
To move beyond a qualitative, case-by-case reading of contracts, the study designs and validates a six-variable weighted scoring instrument, the Shari’ah Substance Test. It scores each contract on Risk Allocation, Depreciation Treatment, Default Handling, Liquidation Rights, Cost Distribution, and Legal Recourse, normalized to a 0–100 composite scale bounded by a weighting constraint summing to 1.00. Scores below 40 indicate significant convergence toward conventional secured-debt treatment; higher bands indicate progressively more authentic risk-sharing.
V. The Architecture of Convergence
5.1 Composite Findings Across the Four Institutions
Clause-level SST scoring produced composite results of 36.65 (Guidance Residential), 35.20 (Lariba/American Finance House), 28.70 (University Islamic Financial), and 23.70 (Devon Bank), for an industry composite average of 31.06. All four scores fall within the same category — significant debt replication — despite differences in institutional structure, regulatory charter, and marketing language across the four providers. All four institutions score within Category III, Significant Debt Replication — a range of just 23.70 to 36.65 out of 100 — despite marketing language built entirely around the vocabulary of equity partnership. COMPOSITE SST FINDINGS, CHAPTERS FIVE & EIGHT
5.2 Institutionalized Debt Convergence (IDC)
The consistency of this result across independently operating institutions points away from an explanation rooted in individual bad faith or an isolated Shari’ah board failure. Institutionalized Debt Convergence describes this pattern as a rational, path-dependent structural equilibrium: alternative financiers operate inside a conventional financial infrastructure built for the management of secured debt, and Basel III capital adequacy mandates, GSE secondary-market liquidity requirements, and UCC Article 9 judicial enforcement norms consistently reward contract terms that behave like debt, regardless of the label attached to the instrument at origination.
Complications of Formal Compliance
6.1 Compliance Substitution
A second structural mechanism, Compliance Substitution, helps explain why existing Shari’ah governance architecture has not corrected this drift. Shari’ah board review is typically concentrated at the point of contract origination, confirming that a document uses appropriate terminology and follows an appropriate contractual sequence, rather than auditing how the contract performs over its full life cycle — particularly during default, foreclosure, and bankruptcy. Formal compliance becomes a substitute for substantive compliance, and the gap between the two widens without any single actor along the chain necessarily intending it.
6.2 Consumer and Regulatory Exposure
For the consumer, the practical consequence is that market risk, cost risk, and default risk remain concentrated on the household in a manner functionally similar to a conventional mortgage, while the institution’s capital position remains comparatively insulated. For regulators and Shari’ah supervisory bodies, the consequence is that origination-stage certification does not, by itself, provide reliable assurance of the treatment a consumer will receive at default.
VII. Toward Substantive Risk-Sharing
The dissertation underlying this paper proposes a Substantive Risk-Sharing Model (SRSM) as a design pathway rather than only a critique. The model is built around three engineering changes: dynamic fair-market-value buyout pricing in place of fixed nominalcost purchase undertakings; proportional allocation of operating and maintenance expenses between institution and client according to actual ownership share; and partnership-oriented default resolution that distributes the consequences of a property’s loss in value according to that same proportional logic, rather than transferring the full burden to the consumer. None of these changes require abandoning the commercial viability of the product; each requires aligning its internal architecture with the equitypartnership principle it is marketed under.
VIII. Conclusion: The Structural Choice Ahead
This research finds that contemporary American Diminishing Musharakah contracts preserve the formal appearance of co-ownership at origination while their internal default architecture reveals systemic convergence with conventional secured credit. This is not evidence of institutional bad faith; it is evidence of a financial and legal environment that structurally rewards debt-like terms regardless of contractual label. The long-term legitimacy of Islamic home finance in the United States will depend on whether the industry is willing to align its operational reality with its philosophical claim — and the Shari’ah Substance Test, together with the Substantive Risk-Sharing Model, are offered here as tools to measure and guide that alignment.
IX. References
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