# *31#[number] on iPhone: Show Your Number (GSM Style) URL: https://byshahid.com/blog/show-your-number-gsm-style-star-31-hash-number-iphone/ App: Secret Codes: IMEI & Carrier (https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322) Author: Muhammad Shahid Updated: 2026-11-04 > *31#[number]: The GSM per-call caller ID override. The GSM equivalent of *82. Presents your caller ID for one call even when your line is set to withhold it. - **Code:** *31#[number] - **What it does:** The GSM per-call caller ID override. - **Published for:** AT&T and T-Mobile - **Type:** GSM networks The GSM per-call caller ID override. This page explains what `*31#[number]` does, how to use it on an iPhone and which carriers it applies to. I build **Secret Codes: IMEI & Carrier**, a free iPhone app with 317 checked codes and guides, including this one. If you would rather tap than memorise, [get Secret Codes on the App Store](https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322). ## What does *31#[number] do? The GSM equivalent of *82. Presents your caller ID for one call even when your line is set to withhold it. ## How do I use *31#[number]? - Open the Phone app and tap Keypad. - Type *31#[number], replacing [number] with the full phone number, including the area code. - Press the green Call button. ## Which carriers does this apply to? | Published for | AT&T and T-Mobile | | Type | GSM networks | | Good to know | GSM networks only. If it does not take effect, use *82 instead. | _Screenshot: The Secret Codes detail screen shows the steps, the carriers and an Open in Phone button._ ## Related caller id codes - [#31#[number]: Hide Your Number (GSM Style)](/blog/what-is-31-code-iphone/) - [*#30#: Check Incoming Caller ID Service](/blog/check-incoming-caller-id-service-star-hash-30-iphone/) - [*#31#: Check Caller ID Setting](/blog/check-caller-id-setting-star-hash-31-iphone/) - [*#76#: Check Connected Line Presentation](/blog/check-connected-line-presentation-star-hash-76-iphone/) - [*82[number]: Show Your Number For One Call](/blog/show-your-number-for-one-call-star-82-number-iphone/) - [*#77#: Check Connected Line Restriction](/blog/check-connected-line-restriction-star-hash-77-iphone/) See all [caller id codes](/blog/iphone-codes/caller-id/) or [every category of iPhone codes](/blog/iphone-codes/). ## How Secret Codes helps Secret Codes keeps this and every other entry a search away. Pick your carrier once and each entry says whether it is published for your line. You can save favourites, add a private note, and record whether a code worked on your line. This entry is part of Secret Codes Pro. **Secret Codes: IMEI & Carrier** is free on the App Store: https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322 ## FAQ ### What does *31#[number] do on iPhone? The GSM per-call caller ID override. The GSM equivalent of *82. Presents your caller ID for one call even when your line is set to withhold it. ### What are the steps for *31#[number]? 1. Open the Phone app and tap Keypad. 2. Type *31#[number], replacing [number] with the full phone number, including the area code. 3. Press the green Call button. ### Where do I use *31#[number]? On the keypad of the Phone app. ### How do I add the number to *31#[number]? Replace [number] with the full phone number, including the area code, then press Call. ### Is *31#[number] a hidden or secret code? No. It is a standard GSM code, handled by the network rather than by a hidden menu on the iPhone. ### Which carriers does *31#[number] work on? It is published for AT&T and T-Mobile. GSM networks only. If it does not take effect, use *82 instead. ### Does *31#[number] work on Android phones too? GSM codes are a network standard, so they generally behave the same on any phone on a network that supports them. ### Will *31#[number] work outside the US? It depends on the network you are on. GSM codes are a standard, but each network decides which it supports. ### What if *31#[number] does not work on my iPhone? Check that it applies to your carrier first, because carriers decide which services they offer and can change them. If it should apply to your line, contact your carrier. ### What is related to *31#[number]? #31#[number]: Hide Your Number (GSM Style). The GSM per-call caller ID block. ### What else is in this category? *#30#: Check Incoming Caller ID Service. See whether you are able to receive caller ID. ### Can I find *31#[number] in an app? Yes. Secret Codes, a free iPhone app, includes it with its steps and carrier details, as part of Secret Codes Pro. ## Sources - [3GPP TS 22.030: Man-Machine Interface of the phone](https://www.3gpp.org/dynareport/22030.htm) - [Apple Support: iPhone User Guide](https://support.apple.com/guide/iphone/welcome/ios)