Short answer
There is no single law. Rome I Article 14 deliberately splits the assignment into separate relationships and applies different laws to each.
- Assignor and assignee — the relationship between the original creditor and the debt collector is governed by the law applicable to their contract, determined under Rome I in the ordinary way.
- The claim itself, and the debtor — the law governing the assigned claim determines assignability, the relationship between assignee and debtor, the conditions under which the assignment can be invoked against the debtor, and whether the debtor's obligations have been discharged.
- Third-party proprietary effects — who owns the claim as against competing assignees, the assignor's insolvency estate or execution creditors — is not governed by Rome I, and no uniform EU instrument has been adopted.
For a practical example: a Dutch supplier issues an invoice to a Belgian customer under a supply contract governed by Belgian law, and assigns it to a German collection agency under an agreement governed by German law. German law governs the supplier-agency relationship. Belgian law governs whether the invoice was assignable at all, what defences the customer has, what notice is needed, and whether paying the original supplier discharges the debt.
The agency's own law is largely irrelevant to the debtor.
The statutory split
"1. The relationship between assignor and assignee under a voluntary assignment or contractual subrogation of a claim against another person (the debtor) shall be governed by the law that applies to the contract between the assignor and assignee under this Regulation. 2. The law governing the assigned or subrogated claim shall determine its assignability, the relationship between the assignee and the debtor, the conditions under which the assignment or subrogation can be invoked against the debtor and whether the debtor's obligations have been discharged. 3. The concept of assignment in this Article includes outright transfers of claims, transfers of claims by way of security and pledges or other security rights over claims." —
The structure reflects a sound policy. The debtor did not choose the assignee and should not have its position worsened by a transaction it was not party to. So everything touching the debtor stays with the law the debtor already signed up to.
Article 14(3) is broad: it covers outright sales of receivables, assignments by way of security, and pledges. Factoring, invoice discounting, securitisation and debt purchase all fall within it.
What the claim's law decides
This is the list that matters for anyone buying or collecting receivables.
Assignability. Whether the claim can be assigned at all, and the effect of an anti-assignment or non-assignment clause in the underlying contract. Member States differ significantly on whether such clauses render an assignment void, merely breach the contract, or are ineffective against certain classes of assignee. This is the single most important diligence point when acquiring a portfolio of invoices from multiple jurisdictions.
Notice and perfection as against the debtor. Whether notice to the debtor is required, who must give it, in what form, and what happens before it is given.
Debtor's defences. The debtor generally keeps against the assignee the defences it had against the assignor — disputes about the goods or services, defective performance, price reductions, and so on. The claim's law fixes the cut-off point for defences arising after assignment.
Set-off. Whether the debtor can set off a cross-claim against the assignor against the assigned invoice is determined by the claim's law under the Article 14(2) heading of the assignee-debtor relationship.
Discharge. Whether payment to the original creditor discharges the debtor once an assignment has occurred, and from what moment. This is the provision that protects a debtor who pays the supplier in good faith without knowing of the assignment.
Interest and recovery costs. Interest on a commercial debt is a matter for the claim's law, including any national implementation of the Late Payment Directive 2011/7/EU.
Limitation. Under Article 12(1)(d) limitation belongs to the law governing the contract — so the invoice's limitation period travels with the invoice, not with the collector.
The gap: third-party effects
Article 14 does not answer the question that matters most in an insolvency: as between two competing assignees of the same receivable, or between an assignee and the assignor's liquidator, who wins?
That is the proprietary or third-party effect of the assignment, and Rome I leaves it out. The Commission proposed a dedicated instrument in 2018 — a Regulation on the law applicable to the third-party effects of assignments of claims, COM(2018) 96 — accompanied by an impact assessment and a public consultation.
That proposal has not been adopted. The legislative record shows it as a pending proposal rather than enacted law.
Until an instrument is in force, third-party effects are determined by the private international law of the forum, and Member States do not agree. Different national approaches point variously to the assignor's habitual residence, the law of the assigned claim, or the law of the assignment contract. The same portfolio can therefore have different proprietary outcomes depending on where insolvency proceedings open.
Related instruments cover adjacent ground without filling the gap. The Insolvency Regulation 2015/848 deals with applicable law in insolvency proceedings and the protection of third parties' rights in rem. The Financial Collateral Directive and securities-specific rules address particular asset classes. None of them supplies a general rule for assigned trade receivables.
This is an open risk to be priced and structured around, not a technicality.
Practical consequences for receivables buyers
Diligence per underlying contract, not per portfolio. Anti-assignment clauses and assignability rules are determined by each invoice's own governing law. A portfolio spanning eight Member States requires eight assignability analyses.
Check for anti-assignment clauses in the supply terms. Standard purchasing conditions frequently contain them, and the consequences vary by jurisdiction.
Give notice in the form the claim's law requires. Notice given in the form the assignee's own law requires may be ineffective.
Expect the debtor's defences to survive. Buying an invoice does not launder a dispute about the underlying goods or services.
Model the insolvency scenario explicitly. Because third-party effects are unharmonised, ask where the assignor's centre of main interests is and what that forum's conflict rules say about competing claims to the receivable.
Do not rely on your own law. The collection agency's governing law governs its contract with the creditor and almost nothing that the debtor cares about.
Practical consequences for debtors
Payment instructions are not self-executing. A letter from a collection agency does not by itself transfer the debt. Whether the assignment can be invoked against you, and whether you are discharged by paying the agency, is determined by the law governing your own contract with the supplier.
Ask for evidence. A debtor is entitled to be satisfied that the assignment occurred and that it has been validly notified in accordance with the applicable law.
Your defences and set-offs survive. Assignment does not cure a defective delivery or extinguish a cross-claim that arose before the cut-off under the claim's law.
Paying the wrong party is your risk. Where an assignment has been validly notified, paying the original supplier may not discharge you. Where it has not, paying the supplier usually does. Establish which position you are in before paying.
Operational checklist
- Identify the law governing the underlying contract that created the invoice.
- Identify separately the law governing the assignment or collection agreement.
- Apply the claim's law to assignability, anti-assignment clauses, notice, defences, set-off and discharge.
- Apply the claim's law to interest, recovery costs and limitation.
- Treat third-party proprietary effects as unharmonised and analyse the relevant forum's conflict rules.
- Assess insolvency risk by reference to the assignor's likely insolvency forum.
- For debtors: verify the assignment and the validity of notice before redirecting payment.
- Monitor whether the 2018 proposal, or any successor, is adopted.
Conclusion
Rome I Article 14 answers the assignment question by refusing to give one answer. The assignor-assignee contract has its own law; everything affecting the debtor stays with the law of the assigned claim; and the proprietary question of who owns the receivable against the world is left outside the Regulation entirely.
For a debt collector operating across borders, that means the invoice's own governing law does most of the work, and the collector's law does very little. For anyone buying receivables, the unharmonised third-party effects remain the significant legal risk — one the EU identified in 2018 and has not yet legislated away.
Sources
This article provides general legal information, not advice for a specific matter. Laws, facts and procedural deadlines may change the result. Follow the linked primary sources and obtain local advice before acting.