Site Control Due Diligence: What Tax Equity Investors Check Before Closing

The Q4 tax equity calendar

Tax equity is the dominant financing mechanism for utility-scale solar and wind in the United States. The market exceeds $20 billion annually according to estimates from Lawrence Berkeley National Laboratory and private market analysts including Wood Mackenzie — and the overwhelming majority of that capital deploys in a single quarter. October, November, and December account for roughly 60–70% of annual tax equity volume.

The reasons are structural. Tax equity investors — primarily large banks and insurance companies — optimize their tax credit utilization against their own fiscal year positions. Under IRC Sections 48 (ITC) and 45 (PTC), a project must be "placed in service" to generate credits in a given tax year. That creates a hard annual deadline. Developers who miss the December 31 in-service date lose a year of credit benefit, potentially triggering resizing or repricing conversations with the investor.

The safe harbor framework softens this somewhat. Treasury's beginning-of-construction safe harbor (5% physical work test or continuous efforts standard) allows a project to lock in the credit rate applicable to the year construction begins rather than the year it completes. For IRA-era projects, this means developers who began construction in 2024 or 2025 may be relying on a safe harbor position that needs to survive diligence scrutiny too. But safe harbor or not, the practical Q4 concentration remains: most developers target year-end closes, and most tax equity investors expect to be fully through diligence by late October to accommodate a December close.

That calendar creates a specific preparation window. If your project is targeting a Q4 2026 tax equity close, your site control evidence package needs to be in diligence-ready form by August 2026. What happens between August and October — investor engagement, IE engagement, title work, investor counsel review — takes time even when there are no deficiencies. When deficiencies surface, it can take weeks or months to cure them. Deals that enter diligence with unresolved site control issues in October do not close in December.

Who is in the diligence chain

Tax equity diligence on site control involves at minimum five distinct parties, each reviewing different pieces of the evidence package with different objectives. Understanding what each party checks — and what they do not check — is essential for structuring a complete package.

Developer and developer's counsel

The developer assembles the initial evidence package and warrants its completeness. Developer's counsel (typically a project finance or energy law firm) reviews the instruments for enforceability, term adequacy, and consistency with the interconnection application. They are also responsible for flagging any issues with the instrument chain — subordination agreements, lender consent requirements, estoppel certificates — that will need to be resolved before close. Developer's counsel does not verify that the instruments actually cover the correct parcels in the GIS sense; that falls to the IE.

Tax equity investor and investor's counsel

The investor engages its own outside counsel (investor counsel) to conduct independent legal diligence on the site control instruments. Investor counsel reviews: instrument enforceability, term adequacy, title insurance exceptions, recording status, and any provisions that could allow a third party to extinguish or subordinate the developer's rights. They are not GIS auditors, but they will flag issues raised by the IE and require legal resolution as a condition to closing.

Independent engineer

The independent engineer is the party most likely to catch site control deficiencies that the lawyers miss. IEs review the site control package through a technical lens: do the instruments described in the legal evidence package actually correspond to the parcels needed for the project footprint? Post-FERC Order 2023, IEs are increasingly expected to do this work quantitatively — running or reviewing a GIS-based coverage computation rather than simply confirming that a lease binder exists. The IE's report is typically attached as an exhibit to the tax equity commitment letter and is a hard deliverable for financial close.

Specifically, the IE checks: (a) that instruments identify and cover the parcels in the interconnection application or IA exhibit; (b) that options-to-lease have been exercised and converted to executed instruments; (c) that instruments are recorded and appear in the county recorder's system; (d) that no instrument expires before projected COD plus a cushion (typically one year); and (e) that RTO-stage coverage thresholds are met at the project's current queue position. On point (e), see below — this is where Order 2023 changed the analysis materially.

Title company

The title company issues a title commitment (typically ALTA form) covering the project site. Title diligence surfaces encumbrances, liens, competing claims, and recording defects that may not appear in the instrument binder. Title exceptions — items the title company is unwilling to insure over — require resolution as conditions to close. A recording gap (executed lease not recorded) typically generates a title exception until the recording is completed.

Coverage reports — parcel-level GIS audits with RTO-stage percentage computations and encumbrance schedules — are becoming standard deliverables in tax equity diligence, not exceptional ones. IEs who previously accepted a lease binder as sufficient confirmation of site control are now expected to verify the computation.

The IE's site control review: what changed post-Order 2023

Before FERC Order 2023, site control review in tax equity diligence was largely a legal exercise. Investor counsel confirmed that the developer had executed leases covering the project footprint, that the leases were recorded, and that the terms were sufficient. The IE might review the lease binder for consistency with the interconnection application, but a quantitative coverage computation — parcel map, acreage calculation, percentage of project footprint covered — was not a standard deliverable.

Order 2023 changed the underlying regulatory structure in a way that made qualitative review insufficient. RTOs now define graduated, stage-specific coverage thresholds — typically 50% at application, 90% at system impact, 100% at IA execution — with specific rules about which instrument types qualify at each stage. An investor whose project entered the PJM queue at 100% coverage with options may now be below threshold at IA execution if those options were never converted to executed leases. An investor whose CAISO project has 92% executed-lease coverage may still fail if Williamson Act parcels are filtered out under CAISO's encumbrance policy.

These are not issues that surface in a legal review of a lease binder. They require a GIS audit: loading all instruments, mapping them to the parcel layer for the project footprint, applying the RTO's eligibility and encumbrance filters, and computing the resulting coverage percentage. For a full reference on the stage-specific thresholds by RTO, see FERC Order 2023 Site Control Coverage Thresholds by RTO and Stage.

The practical consequence: IEs on Q4 2026 deals are asking for coverage reports, not lease binders. Developers who show up with a spreadsheet of lease dates and a PDF folder are creating friction in the diligence process even when their actual coverage is adequate. Developers who produce a coverage report — with a parcel map, computed coverage percentage at current RTO stage, and an encumbrance schedule flagging any disqualifying conditions — accelerate the IE's work and reduce the risk of a last-minute finding.

For a detailed look at how FERC Order 2023 compliance obligations are evolving in 2026, see FERC Order 2023 Compliance in 2026: Why This Is the Year.

The 6 most common deal-killers

Most tax equity site control diligence problems fall into one of six categories. None of them are obscure. All of them are curable if caught early. The problem is that developers frequently discover them at the diligence phase rather than before it.

1. Option-to-lease not converted at financial close

An option-to-lease gives the developer the right to execute a lease but is not itself an executed lease. Tax equity investors and their counsel want recorded, executed leases at financial close — not options. The rationale is straightforward: an option can be allowed to lapse, and an investor who holds a tax equity interest in a project whose site control evaporates post-close has a problem.

Under FERC Order 2023, options-to-lease are excluded from coverage calculations at IA execution in every FERC-jurisdictional RTO. This means a project with unconverted options at IA execution is already out of compliance at the interconnection level — a fact that the IE will identify and that investor counsel will require resolved before close. Developers who haven't exercised options by the time diligence begins face a two-front problem: fixing the interconnection compliance issue and satisfying investor counsel simultaneously.

The timeline for option conversion is not short. Many lease negotiations run months. Start the conversion process well before August if you have unconverted options on a project targeting a Q4 close. For a detailed treatment of how option expirations interact with queue milestones, see Option-to-Lease Expiration and Interconnection Milestones.

2. Lease term expires before COD plus buffer

Tax equity investors require that all instruments remain in effect through the project's anticipated commercial operation date plus a buffer — typically one year, sometimes longer depending on the investor's credit committee requirements. A lease that expires the month after projected COD is a problem. A lease that expires before projected COD is a fatal defect.

This issue arises more often than it should because developers negotiate initial lease terms early in the development process, often before the interconnection timeline is fully understood. Queue delays — which have accelerated significantly post-Order 2023, with FERC's Morgan Lewis analysis noting over $22 billion in project cancellations from grid congestion and queue management issues — mean that originally projected COD dates routinely slip. A lease that looked adequate in 2023 for a 2025 COD may now expire before a 2027 COD.

Every project preparing for Q4 diligence should run a current expiration analysis against the latest COD projection. Identify instruments that expire within 24 months of projected COD and initiate extension negotiations now, before the diligence clock is running.

3. Recording gap — executed but unrecorded instruments

A lease signed by both parties but not recorded in the county recorder's system creates a title insurance problem. The title company cannot insure over an unrecorded instrument without exception, and a title exception on the project site is a condition that investor counsel will require cured before close.

Recording gaps are common for two reasons. First, developers sometimes delay recording to avoid tipping off competitors about project site locations — a legitimate concern in competitive land markets but one that creates a diligence problem. Second, recording in some jurisdictions involves processing times of weeks to months; a lease recorded in September for an October close may not be confirmed in the system before the diligence deadline.

The fix is simple but time-sensitive: record all executed instruments as early as operationally feasible. Do not wait until diligence is imminent. Build a recording confirmation schedule — instrument by instrument, with book/page or document number from the county recorder's system — and include it in your diligence package. This eliminates title exceptions and gives the IE confirmable evidence that instruments exist in the public record.

4. Williamson Act encumbrances for CAISO projects

California's Williamson Act places agricultural land under long-term preservation contracts with local governments. Parcels subject to active Williamson Act contracts cannot be used for solar development without either cancellation (which requires a 50% cancellation fee) or non-renewal (which begins a 9-year rolling term reduction). For CAISO projects, Williamson Act parcels are disqualified from coverage under CAISO's encumbrance policy at system impact study stage and beyond.

A CAISO project with 15% of its parcels encumbered by active Williamson Act contracts can drop from apparent 100% coverage to 85% compliant coverage after encumbrance filtering — potentially falling below the 90% threshold at facilities study or the 100% threshold at IA execution. Tax equity investors and their IEs do not ignore this; Williamson Act status is verifiable through California county assessor records and is a standard item in CAISO project diligence.

Non-renewal notices require filing with the county and begin a 9-year countdown. For a Q4 2026 close on a project targeting COD in 2027 or 2028, Williamson Act parcels that have not yet had non-renewal notices filed are likely to remain encumbered through COD. The solution is either to exclude those parcels from the project footprint (if coverage remains adequate without them), to initiate non-renewal early enough that the encumbrance resolves before COD, or — in rare cases — to pursue cancellation. For more on the workflow, see Williamson Act Land and CAISO Interconnection Queue.

5. Coverage below RTO threshold on GIS audit

This is the deficiency that most often surprises developers — not because the instruments don't exist, but because the computed coverage percentage on a properly filtered GIS audit is lower than expected.

The gap between a developer's self-assessed coverage and the IE's computed coverage typically comes from four sources: (a) instruments that have lapsed or expired and were not removed from the developer's internal tracking; (b) options counted at full weight that are excluded at the current RTO stage; (c) encumbered parcels filtered out under the RTO's encumbrance policy; and (d) parcels where one or more property owners has not signed, making the instrument incomplete. Any of these can cause a project that looks adequately covered in a spreadsheet to fail a rigorous GIS audit.

A developer who has not run a current GIS audit does not know their actual compliant coverage. Running that audit before diligence begins — and resolving any deficiencies — is the single most effective preparation step for Q4. The audit needs to reflect the RTO's current stage rules, not a generic "percent of acreage under lease" calculation.

6. ROFR and subordination provisions

A right of first refusal (ROFR) in a lease or option agreement gives a third party (often the landowner) the right to match any offer for the property before the developer can exercise its interest. If structured as a right that could be exercised to extinguish the developer's lease or option, a ROFR creates title uncertainty that investor counsel will flag as a condition to close.

Similarly, senior liens or mortgages on the underlying property that have not been subordinated to the developer's lease interest create a risk that a foreclosure by a senior lender could extinguish the developer's site control. Investor counsel will require either a subordination, non-disturbance, and attornment (SNDA) agreement from each senior lender, or title insurance coverage over the subordination risk.

These provisions are common in agricultural lease agreements and are often buried in boilerplate. A systematic review of all instruments for ROFR, subordination, and competing interest provisions — before diligence — is essential. Instruments with problematic provisions need to be amended or replaced, which requires landowner cooperation and takes time.

What to have ready before August 2026

A diligence-ready site control package for a Q4 2026 tax equity close requires the following elements. This is not a comprehensive closing checklist — it is specifically the site control component that the IE, investor counsel, and title company will review.

The instrument inventory

A complete, current inventory of all instruments associated with the project: leases, easements, options, ROW agreements, and fee simple interests. For each instrument: parcel number(s) covered, instrument type, execution date, recording date and location (book/page or document number), term start and end dates, option exercise status, and any encumbrance flags. This is the index that every other diligence workstream will reference.

The coverage report

A GIS-based coverage report computed at the current RTO stage. The report must show: project boundary, parcel layer with instrument assignments, coverage percentage after applying the RTO's eligibility and encumbrance filters, and a deficiency schedule identifying parcels that are uncovered or disqualified. If any parcels are excluded due to encumbrances, the report should identify the encumbrance type and status. The IE will either accept this report or run their own audit against it — either way, having it ready accelerates the process and reduces the risk of a surprise finding.

Recording confirmation schedule

For each recorded instrument: county recorder confirmation (book/page or document number), recording date, and county name. If any instruments are executed but not yet recorded, identify them separately with a recording timeline.

Option exercise evidence

For any instrument that originated as an option-to-lease and has since been exercised: the original option agreement, the exercise notice, the executed lease, and recording confirmation. If options remain unexercised, investor counsel will require an explanation and a timeline for exercise before close.

Expiration schedule vs. COD projection

A side-by-side comparison of instrument expiration dates against the project's current projected COD. Any instrument expiring within 24 months of projected COD should be flagged. Any instrument expiring before projected COD is a fatal defect requiring immediate cure or replacement.

Encumbrance schedule

A schedule identifying all parcels subject to Williamson Act contracts, conservation easements, Chapter 61A or 61B classifications (for ISO-NE/Massachusetts projects), agricultural district restrictions, or other encumbrances that may affect coverage qualification under the relevant RTO's rules. For each encumbrance: current status, planned resolution, and timeline.

Title commitment

A current ALTA title commitment covering the project site, with exceptions schedule. Review exceptions against the instrument inventory before delivering to investor counsel — exceptions that can be resolved before close (recording gaps, expired liens) should be cured proactively rather than handed to investor counsel as open items.

Why 2026 is the year to run this proactively

The interconnection queue is under more stress than it has been at any point in the past decade. FERC Order 2023's cluster study transition is generating deficiency notices, withdrawal pressures, and revised study timelines across every RTO. Projects that were on a 2025 COD trajectory are routinely revising to 2026 or 2027. Projects that were at 90% coverage with a comfortable buffer may now be at 85% after encumbrance filtering and option exclusions.

At the same time, the tax equity market is not growing fast enough to absorb the pipeline. Investors have more deal flow than they can close, which means they have leverage to be selective about which packages they take to commitment. A developer who arrives in August with a clean coverage report, no recording gaps, no unresolved encumbrances, and a complete instrument inventory is a developer whose deal gets prioritized. A developer who shows up in October with a lease binder and a spreadsheet is creating work for the IE and investor counsel at the worst possible time.

The mechanics of FERC Order 2023 compliance — the quantitative, stage-specific coverage audit — are not going away. IEs and investor counsel are internalizing this framework. The developers who understand it and operationalize it before diligence begins will have a structural advantage in Q4 closes for the foreseeable future.

Sources

• FERC Order 2023 — Interconnection Final Rule Explainer (FERC.gov)
• Lawrence Berkeley National Laboratory — Electricity Markets & Policy Group (emp.lbl.gov)
• Morgan Lewis — Failure to Connect: Grid Challenges Persist as Demand Rises (2025)

Related articles

• FERC Order 2023 Site Control Coverage Thresholds by RTO and Stage — The full per-stage, per-RTO threshold reference: eligible instruments, option weights, encumbrance policies, and BLM ROW status gates.
• Option-to-Lease Expiration and Interconnection Milestones — How option expirations interact with queue milestones and the conversion timeline that determines whether your coverage holds at IA execution.
• Williamson Act Land and CAISO Interconnection Queue — How California agricultural preserves affect CAISO site control coverage and the non-renewal notice workflow for projects targeting financial close.
• FERC Order 2023 Compliance in 2026: Why This Is the Year — Market analysis, RTO implementation status, deposit escalation math, and the compliance landscape heading into Q4 2026.