[Direct answer]It is invalid and not protected by law. Both paths lead to failure: if the lender knows that the borrowed money is used for gambling but still lends it, the private lending contract is invalid; the IOU issued at the gambling table (conversion of gambling debts) directly violates public order and good customs. Not only will the court reject the case, but it may also transfer the evidence of the violation to the public security organ. For legal lending, two pieces of evidence are essential: the IOU and the actual delivery certificate (transfer records), and neither can be missing.

1. Problem background and typical scenarios

When a gambler is desperate to lose at the card table, he writes a promissory note. The creditor then uses the promissory note to sue him—the promissory note is written in black and white, but this "debt" is fundamentally unethical from the outset. A common misconception in gambling debt disputes is that "having a promissory note guarantees victory." However, the legal validity of a promissory note is completely different from the evidence on paper. The effectiveness of a promissory note never solely depends on the signature, but also on the source and destination of the money involved.

II. Key points of contention

First, the two typical situations where the contract is invalid: lending money to someone who knows they are gambling and providing a promissory note for the gambling debt. Second, the application of the public order and good morals clause in adjudication. Third, the allocation of the burden of proof: what else is needed besides the promissory note. Fourth, the collateral consequences of transferring gambling-related clues to the public security organ.

III. Professional analysis by Henglue Law Firm

Two public cases illustrate the fate of gambling debt promissory notes: In the case heard by the Xiangyin County Court in Hunan, Gan * issued a promissory note for 26,900 yuan to Mah * , the owner of a mahjong parlor. Mah * admitted that some of the borrowed money was used for gambling. The court ruled that Mah * knew the money was intended for illegal activities but still provided the loan, thereby violating public order and good customs. According to the Judicial Interpretation on Civil Lending, if a lender knows or should have known that the borrower used the loan for illegal activities, the civil lending contract is invalid. Since Mah * only held the promissory note and lacked evidence such as bank transaction records to prove legitimate lending, he should bear the legal consequences of failing to provide sufficient evidence, and the court dismissed all his claims. In the case heard by the Yubei District Court in Chongqing, Tang * and others used property as stakes to play cards. After losing money, Tang * was forced to write a promissory note for 12,700 yuan on the spot. The court ruled that gambling is a legally prohibited activity in China. Although the promissory note appears to be a civil loan, the creditor-debtor relationship violates the principle of legality in civil activities and is not protected by law. The court dismissed all Tang *’s claims and referred the relevant illegal clues to the public security authorities for further investigation. These two cases highlight two key rules: 1. **Knowingly lending for gambling** – If the lender knows or should have known about the loan’s purpose, the contract is invalid, and the money cannot be recovered. This is a major pitfall for lenders. 2. **Promissory notes for gambling debts** – Promissory notes written on the spot after losing money in gambling are not legitimate loans but ancillary documents of gambling activities, unprotected by law, and subject to referral of related clues to public security authorities. This is a major pitfall for both gambling participants. **Key burden of proof**: - If the lender claims a debt, the promissory note is only proof of the debt. They must also prove the legitimate and lawful transfer of funds. If the large-scale cash transfer cannot be explained or substantiated, the lender must bear the burden of proof. - If the borrower defends the use of the money for gambling, they can provide evidence such as chat records, witnesses, and police reports. Once the use is confirmed, the contract is invalid. **Practical reminders for borrowers**: - Don’t panic if forced to sign a gambling debt promissory note. Actively defend against the claim by proving the illegal use of the money. Avoid settling debts privately to avoid further entrapment. - For lenders: Verify the purpose of the loan before lending, retain transaction records, and document communication about the loan’s use. Claims of "unawareness" must be supported by evidence. Knowingly lending to illegal activities risks losing even the principal.

IV. Practical suggestions and legal basis

The first step is to verify the purpose of the loan and keep the communication records before lending; the second step is to keep transaction records: transfer the funds with a note, as cash payments of large amounts are inherently less convincing; the third step is to actively defend against accusations: the defendant in a gambling-related promissory note case should actively provide evidence to prove that the purpose of the loan is illegal, and strive to have the contract declared invalid; the fourth step is to cut off the chain: promptly stop losses involving gambling and avoid the secondary harm of usury and violent collection. Main legal basis: Article 153 (Public Order and Good Morals) and Article 155 of the Civil Code of the People's Republic of China; Article 13 of the Supreme People's Court's Interpretation on Several Issues Concerning the Application of Law in the Trials of Civil Loan Cases; the specific application shall be subject to the currently effective provisions.

5. Henglu Law Firm's Advice

There are three key points regarding gambling debts and promissory notes: 1. Lending money to someone knowing they gamble is a violation of the law, rendering the contract invalid and making it difficult to recover the money. 2. Promissory notes written at the gambling table are not legally binding. If the court dismisses the case, the matter will be referred to the authorities for further investigation. 3. A promissory note is just an admission ticket—the actual proof of payment (bank transaction records) is what truly protects your rights. For disputes involving gambling debts and the validity of loans, you can seek legal assistance through the following channels:Creditor's rights and debts, and enforcement casesFor obtaining a comprehensive solution for services, or for debt collection and rights protection related to gambling and criminal activities, you can refer to the relevant information for referenceCriminal defense and criminal case filingFor those whose family assets are burdened by gambling debts, they can seek help from relevant organizations or platforms.Divorce litigation and family disputesFor reference, you can check the guidelines on loan documentsSpecialised legal servicesPlate consultation.

VI. Frequently Asked Questions

Q1: Can a promissory note for gambling debts be used to file a lawsuit?

The right to sue exists, but it's almost impossible to win the case. Gambling debts and IOUs violate public order and good customs and are not protected. The court will reject the case and may transfer the clues related to gambling to the public security organ for handling.

Q2: If I don't know that the other party borrowed the money to gamble, is the promissory note still valid?

If the lender genuinely did not know and should not have known that the funds were lawfully delivered, the loan is valid; if the lender knew or should have known that the funds were used for gambling, the contract is invalid.

Q3: Can you win the case even if you only have a promissory note but no transfer record?

For large-amount loans, the risk of winning a lawsuit is extremely high only with a promissory note. The delivery receipt is a crucial piece of evidence, and for cash delivery, it's necessary to explain the source of the funds and the process of the delivery.

Q4: Do I still have to pay off the gambling debts?

It's not legally binding — gambling debts are not protected by law. If you encounter violent collection efforts, you should promptly report the matter to the police and seek legal redress.

Q5: What should I do if I'm forced to write a promissory note for a gambling debt?

Keep the evidence of coercion, actively defend against the lawsuit if the defendant's actions are illegal, and report the case to the police if necessary. It is crucial to avoid settling the matter privately, as this may lead to falling into the trap of secondary lending.

The above questions and answers are mainly based on the judicial practice in Beijing. There may be differences in the interpretation of the law in different regions. It is recommended to consult a professional lawyer based on the specific circumstances of the case.

VII. Relevant public cases (for reference only, not handled by our firm)

The following cases are all sourced from the official websites of courts at all levels, judicial authorities, and authoritative media outlets that have been publicly released. They are unrelated to the cases handled by our firm and are provided solely for reference in understanding relevant adjudication rules. They do not constitute opinions on specific cases.

[Case No.]The case number has not been made public.
[Trial Court]The People's Court of Xiangyin County, Hunan Province
[Judicial Summary]Gan * issued a promissory note for 26,900 yuan to Ma *, the operator of the mahjong parlour, who admitted that some of the borrowed money was used for gambling. The court held that Ma * knew the money was used for gambling but still provided the loan and obtained illegal benefits, which violated public order and good morals. According to the Judicial Interpretation of Private Lending, if the lender knows or should have known that the borrower used the loan for illegal and criminal activities but still provided the loan, the private lending contract shall be invalid. Ma * only held a promissory note and no bank transaction records as evidence to prove the legitimacy of the loan, and should bear the legal consequences of failing to provide evidence. The court ruled to dismiss all of his claims.
[Source]China Court Network, August 2025 (2025-08)

[Case No.]The case number has not been made public.
[Trial Court]The People's Court of Yubei District, Chongqing City
[Judicial Summary]Tang ** and Ren **, among others, played cards with money as stakes. After Ren ** lost money, he was forced to write a IOU for 12,700 yuan on the spot. The court held that gambling is an illegal act prohibited by national law. Although the IOU issued for gambling debts appears to be a private loan, the creditor-debtor relationship between the two parties violates the principle of legality in civil activities and is not protected by law. The court ruled to dismiss all of Tang **'s claims and referred the relevant illegal clues to the public security organ for handling in accordance with the law.
[Source]China Court Online, September 2022 (2022-09)

If you are facing similar problems, it is recommended that you consult a professional lawyer as soon as possible with the evidence materials, so as to avoid missing the statutory time limit. →\nLegal services for creditor-debtor disputes·Beijing Henglu Law Firm

Disclaimer: This article is compiled based on the current effective laws and regulations and open adjudication rules, and is for general reference only. It does not constitute a formal legal opinion on specific cases. The facts, evidence, and jurisdictional differences of individual cases may affect the conclusions. If you encounter disputes, please consult a practicing lawyer in time.