Your O2 SIM number is printed on the back of the physical SIM card itself, usually a 19-digit code starting with 89 (this is the ICCID, or SIM serial number). If you want your O2 mobile phone number rather than the SIM serial, that is a different thing entirely, and there are several quick ways to retrieve it. Both are covered below.
These two things get confused regularly. The SIM card number (ICCID) is the 19-digit identifier printed on the card itself, starting with 89. O2 uses it internally to identify the SIM. Your mobile number (sometimes called the MSISDN) is the 11-digit number people actually call or text. Most of the time, when someone asks "what is my O2 SIM number?", they mean the mobile number, not the ICCID.
Look at the back of the physical SIM card. The 19-digit number is printed there directly. If your SIM came on a larger plastic card (the credit-card-sized holder), the number is also printed on that holder, so keep the packaging until you are sure the SIM is working.
If the SIM is already in your phone and you have lost the packaging, go to your phone's settings. On Android, go to Settings, then About Phone, then SIM Status. On iPhone, go to Settings, then General, then About, and look for ICCID. The exact path varies slightly by device model, but those menus are consistent across most handsets in 2026.
You do not need any credit to check your own number. The simplest method is to dial 4445 from your O2 SIM. O2 will send you a free text message with your mobile number. This works on both Pay As You Go and Pay Monthly.
Alternatively, dial *#100# and press call. On most O2 handsets this triggers a free SMS with your number. If neither shortcode works on your specific handset, try texting INFO to 2020 from the O2 SIM, which is also free.
Log in to the My O2 app (available on iOS and Android) or visit my.o2.co.uk. Once signed in, your mobile number appears on the main account dashboard. This is useful if you have a new SIM that has not yet received any texts, or if you are setting up a second line and cannot remember which number belongs to which SIM.
An unactivated SIM will not respond to shortcodes. In that case, the ICCID on the card is the only number available to you until activation is complete. When you activate through O2's website or the My O2 app, you will be asked to enter the ICCID, so have the card to hand. Once activation is confirmed, the shortcode methods above will work normally.
If every other method fails, call O2 customer service on 202 (free from an O2 mobile) or 0344 809 0202 from any other phone. The adviser can confirm your mobile number after a quick security check. O2's customer service line is open daily, and wait times tend to be shorter early in the morning.
## Frequently asked questions ### where is my O2 SIM number Your O2 SIM number (ICCID) is a 19-digit code printed on the back of your physical SIM card, starting with 89. If your SIM came on a larger plastic card holder, the number is also printed there. Keep the packaging until you're sure the SIM is working, as you'll need it to find this number if the SIM is already in your phone. ### how to find O2 mobile number without balance You can find your O2 mobile number by checking your phone's settings even without credit or balance. On Android, go to Settings > About Phone > SIM Status. On iPhone, go to Settings > General > About and look for ICCID. Your mobile number (MSISDN) is the 11-digit number people call, which is different from your 19-digit SIM serial number. ### what is the difference between SIM number and phone number O2 Your O2 SIM number (ICCID) is a 19-digit identifier printed on the card itself starting with 89, used internally by O2. Your phone number (MSISDN) is the 11-digit number people actually call or text you on. Most people asking for their SIM number actually mean their mobile phone number, not the ICCID. ### how to check O2 SIM number on phone If your SIM is already in your phone, you can find the ICCID in your settings without needing the physical card. On Android, navigate to Settings > About Phone > SIM Status. On iPhone, go to Settings > General > About and scroll to find ICCID. The exact menu path may vary slightly depending on your device model. ### O2 SIM card number 19 digits where to find The 19-digit O2 SIM number starts with 89 and is printed directly on the back of your physical SIM card. If you've already inserted the SIM into your phone and lost the card packaging, you can retrieve this number from your phone's settings under SIM Status (Android) or About (iPhone). ## Sources 1. [How do I find my O2 SIM number How to check O2 ... - YouTube](https://www.youtube.com/watch?v=3lK1EEiNTDI) (www.youtube.com)