Once a year, check how many SIM cards and bank cards are registered in your name; investigate and close any you did not open

No charge. Check SIM cards through the 工信微报 WeChat account or Alipay's 一证通查 mini program; check bank cards using 一键查卡 in the UnionPay 云闪付 app. Each form takes a few minutes, with results notified by SMS within one or two days. The difficulty is remembering to do it once a year without a reminder.

China's Anti-Telecom and Online Fraud Law requires telecom authorities to provide convenient channels for users to check SIM-card information registered in their names. The People's Bank of China and other authorities must provide convenient channels for customers to check bank and payment accounts in their names. The nationwide 一证通查 mobile-SIM inquiry service, guided by the Ministry of Industry and Information Technology, launched on 14 September 2021. Using an identity card, users can check the number of SIM cards registered in their names and their carriers. It was introduced after anti-fraud investigations found that some SIM cards involved in crimes had been opened using other people's identities without their knowledge, potentially affecting their personal credit. Results arrive within 48 hours by SMS from 10699000. If the count does not match, ask the carrier for details; with the user's authorization, it can verify, unlink, suspend or close the accounts. 一证通查 2.0 launched in July 2022. A phone number and the last six digits of an identity-card number let users check how many internet accounts are linked to the number. At launch it supported companies including Tencent, Alibaba, Baidu, Kuaishou, Douyin, JD.com and Meituan, and reported counts only. For bank cards, China UnionPay extended 一键查卡 in its 云闪付 app to all mainland provinces and municipalities on 29 June 2022. Select the banks and complete identity verification to submit an inquiry. A report is generated within 24 hours, with card details masked, and is automatically deleted after 7 days. This service is nationwide in China.

全国人大常委会 (2022). 反电信网络诈骗法（第十条、第十六条）. https://www.spp.gov.cn/spp/fl/202209/t20220902_575631.shtml；人民网 (2021). 工信部推出「一证通查」服务：可查询用户名下电话卡数量. 中国政府网转载，2021-09-15. http://app.www.gov.cn/govdata/gov/202109/15/475868/article.html；新华社 (2022). 工信部推出「一证通查2.0」服务. 福建省工业和信息化厅转载，2022-07-22. https://gxt.fujian.gov.cn/zwgk/xw/jxyw/202207/t20220722_5958108.htm；中国银联 (2022). 云闪付APP「一键查卡」功能面向境内所有省市开放. https://cn.unionpay.com/upowhtml/cn/templates/newInfo-nosub/7885004da382485e8bde5a0ba000fdd3/20220629145824.html

一键查卡 checks UnionPay cards only. At the time, UnionPay explained that cards with no phone number on file at the bank or an expired identity document could not yet be found. The issuing bank's records are authoritative: a missing result does not prove there is no card. For loans or credit cards opened using your identity, check your credit report; see Item 9 in Section 8 (credit reports). If 一证通查 2.0 shows many linked accounts, unlink them before changing or cancelling the number; see Item 12 (before giving up an old phone number). Lending or selling your own cards to someone else is a separate matter; see Item 8 in Section 8 (do not hand over bank cards or SIM cards). This is grade C because the sources are official service descriptions, with no study estimating how much loss these checks prevent. The benefit magnitude is judged medium. The beneficiary is you.