# United Kingdom Messages containing sexual/adult content are prohibited. Marketing messages should also have a clear opt-in and opt-out procedure. The use of International Numbers for A2P messages is being blocked by the UK Mobile Network Operators. In addition, unauthorized variants of legitimate SenderIDs, i.e. SIDs belonging to banks and government agencies as well as generic, non-branded Sender IDs (eg. “Verify”, ”OTP”, ”Code”, etc.), are also being filtered. Therefore it is required to use a branded, Alphanumeric SID and/or UK Domestic numbers for your A2P messages. #### **Sender ID Registration** If you would like to continue sending SMS to the United Kingdom, you will need to [submit an approval request form](https://dashboard.messagebird.com/en/settings/sms) and whitelist all the Sender IDs that you use. Instructions on how to submit the form can be found in this [Help Center article](/connectivity-platform/getting-started/requesting-access-for-restricted-countries.md). From **June 12th, 2023**, MessageBird will start **BLOCKING** **all NEW unregistered SMS Sender IDs going to the United Kingdom**. \ If you have any questions, [please contact Customer Support](https://support.messagebird.com/hc/en-us/requests/new). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.bird.com/connectivity-platform/country-restrictions-and-regulations/united-kingdom.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.