Solar Supply Chain Due Diligence in 2026: Forced Labour Rules, UFLPA and Traceability
By PVFirms Editorial Team, Published on 2026-10-24 • 7 min read
Buying solar modules now comes with a compliance question: can you show where the silicon inside them came from? In the US, modules have been held at the border under the Uyghur Forced Labor Prevention Act (UFLPA) since 2022. In the EU, the Forced Labour Regulation will apply from December 2027, and many buyers are already writing traceability requirements into contracts. Solar supply chain due diligence has moved from an ESG report appendix to a procurement gate.
This guide is for procurement managers, developers, EPCs and distributors. It summarises the main rules, explains why polysilicon sits at the centre of the issue, and lists the documents worth requesting from suppliers.
In short:
- The UFLPA presumes that goods linked to Xinjiang or to listed entities are made with forced labour, and importers must rebut that with evidence.
- The EU Forced Labour Regulation bans products made with forced labour from the EU market from 14 December 2027.
- The EU's broader due diligence directive (CSDDD) was postponed and scaled back through the 2025 Omnibus package, so check the final text.
- Real module traceability means mapping every tier from polysilicon to module, backed by documents per shipment.
Why polysilicon is the focal point
A crystalline module passes through several stages: metallurgical silicon, polysilicon, ingot and wafer, cell, and finally module assembly. Polysilicon production is heavily concentrated in China, including in Xinjiang, where forced-labour concerns have been documented by governments and investigators.
The key point for buyers is that the assembly location says little about the silicon. A module assembled in South-East Asia, Europe or the US can still contain polysilicon from anywhere. Polysilicon capacity outside China exists, for example in Germany, the US and Malaysia, but it is small relative to global demand, so traceable supply chains usually cost more and come in limited volumes. Other materials, such as aluminium for frames, have also drawn regulators' attention.
The rules side by side
| US UFLPA | EU Forced Labour Regulation | EU CSDDD | |
|---|---|---|---|
| Status | In force since June 2022 | Adopted 2024, applies from 14 December 2027 | Adopted 2024, delayed and under revision via the 2025 Omnibus |
| Who it targets | Importers into the US | Any operator placing products on, or exporting from, the EU market | Large companies, through their own due diligence process |
| Mechanism | Rebuttable presumption; customs detain or exclude goods | Investigations by national authorities or the Commission; bans and withdrawals | Duty to identify and address human rights and environmental harms |
| Burden of proof | Importer, with clear and convincing evidence | Authorities build the case; operators must supply information | Company's own process and reporting |
US: the UFLPA
US Customs and Border Protection enforces the Act. Goods made wholly or partly in Xinjiang, or by entities on the UFLPA Entity List, are presumed to be made with forced labour and barred from import unless the importer proves otherwise. Polysilicon is a stated enforcement priority, and solar shipments have been detained when importers could not document the full chain.
EU: the Forced Labour Regulation
The Regulation applies to all products and all company sizes, with no presumption tied to a region. Authorities take a risk-based approach and, where forced labour is established, can order products to be withdrawn from the EU market and disposed of. The Commission is due to publish guidance and a database of risk information to support operators. Check what has been released before you finalise internal procedures.
EU: CSDDD and national laws
The Corporate Sustainability Due Diligence Directive was adopted in 2024. The 2025 Omnibus simplification package first postponed its application and then moved to narrow its scope and obligations. Thresholds and dates have shifted during negotiations, so rely only on the final adopted text. National laws, such as Germany's Supply Chain Due Diligence Act, also remain relevant but are being adjusted, so confirm their current status.
Solar module traceability: documents to request
Supplier declarations and codes of conduct are a starting point, not evidence. For each order, ask for:
- A supply chain map naming the factory and address for each tier, from polysilicon to module, for the specific production batch.
- The chain of custody method, whether segregated or mass balance, and who audited it.
- Transaction records such as purchase orders, invoices and shipping documents linking polysilicon lots to wafer and cell batches.
- Production records that tie module serial numbers to cell and wafer lots.
- Independent traceability audit reports, and participation in industry schemes such as the Solar Stewardship Initiative launched with SolarPower Europe, where available.
- Material testing, such as isotopic analysis by specialist laboratories, as a supplementary check rather than a substitute for documents.
Building due diligence into ESG solar procurement
Pre-qualification. Add a traceability questionnaire to the RFP and score it, rather than treating it as a pass or fail tick box.
Contracts. Include representations on origin, a duty to deliver traceability documents with each shipment, audit rights, rights to reject and replace, and indemnities covering detention, storage and delay costs. If an EPC buys the modules, flow these clauses down. Our EPC tender checklist shows where they fit.
Beyond modules. Inverters and batteries have their own supply chain risks. The EU Batteries Regulation includes separate due diligence requirements, although its timelines have also moved.
Price and lead time. Traceable modules can carry a premium and longer lead times. Plan for both, and avoid relying on a single supplier.
A Tier-1 label is a bankability indicator, not a traceability certificate. The PVFirms explainer on Tier-1 solar panels sets out what the label means, and the guide on how to choose a solar panel manufacturer covers wider supplier criteria.
Where supplier verification fits, and where it stops
Supply chain due diligence starts with knowing who you are dealing with. PVFirms verification confirms a company's identity, business registration and VAT details against official registers, plus at least one live customer. The Premium Partner tier adds liability insurance, independent client references, ISO 9001 or equivalent, and an editorial inspection.
That helps with counterparty checks, but it is not a forced-labour audit and does not verify where a manufacturer's polysilicon comes from. Use the manufacturer directory, which lists 654 manufacturers as of October 2026, to build a long list, then apply your own traceability requirements. If you buy through wholesalers, our guide to solar panel wholesale suppliers in Europe explains how distributors fit into the chain.
FAQ
When does the EU Forced Labour Regulation apply to solar?
The Regulation applies from 14 December 2027 and covers all products, including modules, inverters and batteries. From that date, products found to involve forced labour can be banned from the EU market and withdrawn. Many buyers are building traceability into contracts now so their supply is compliant before the date arrives.
Do UFLPA rules affect solar projects in Europe?
Not directly, as the UFLPA governs imports into the US. Its indirect effect is significant, however. Several large manufacturers run separate, documented supply chains for the US market. European buyers can ask which chain their modules come from and request the same documentation.
Is a Tier-1 module automatically free of forced labour risk?
No. Tier-1 lists reflect a manufacturer's financing track record, not the origin of its materials. A Tier-1 supplier may source polysilicon from several places, and the mix can change between batches. Ask for batch-level traceability documents regardless of a manufacturer's tier status.
Do small installers need solar supply chain due diligence?
Under the EU Forced Labour Regulation, obligations do not depend on company size, although authorities consider size and resources. In practice, importers and distributors will pass documentation requirements down the chain. Smaller installers should keep supplier records and buy from distributors who can provide traceability documents on request.
Put traceability into your next tender
Add the six document requests above to your next RFP and make delivery a contract condition. Then build your supplier long list in the PVFirms manufacturer directory and screen each candidate against your traceability requirements.