What happens to your phone number after you stop using it

Key points

• When you give up a mobile number, the carrier holds it for a while and then gives it to someone new. In the US the rules allow a holding period of 45 to 90 days for residential numbers. In India, TRAI told the Supreme Court a deactivated number isn't reallocated for at least 90 days.
• The new owner can receive texts meant for you, including login codes and password resets. Princeton researchers found most recycled numbers they sampled were still linked to accounts or leaked credentials.
• Before you let a number go, move every account to a new number or a non-SMS factor. If you use a number for verification, keep it renewed for as long as any account depends on it.

Phone numbers are a limited resource. When you cancel a plan, let a prepaid SIM run out or switch numbers, your old number doesn't disappear. After a holding period it goes back into the pool and is given to someone else. That's number recycling, and it's normal. It only becomes a problem because so many accounts still treat "whoever holds this number" as "the account owner".

This guide explains what happens to a number after you stop using it, how long it takes, what researchers found when they tested recycled numbers, and how to protect yourself before you let one go.

The life cycle of a disconnected number

1. Disconnection. You cancel, port out, or the carrier deactivates the number for non-payment or non-use.
2. Aging (holding) period. The number is set aside and not given to anyone. This gives callers and services time to notice the change.
3. Back in the pool. Once the aging period ends, the number can be assigned to a new customer.
4. New owner. Someone gets "your" old number and starts receiving whatever is still sent to it: calls, texts and verification codes.

United States

US rules define aging numbers as disconnected numbers that aren't available for assignment for a set period. For residential numbers that period is at least 45 days and at most 90 days. Business numbers can be held for up to 365 days. That's set out in 47 CFR 52.15(f)(1)(ii).

Carriers describe their practice in line with that rule. T-Mobile says it holds numbers for a minimum of 45 days and up to 90 days before they become available for reuse. Verizon says federal regulations require it to wait 45 days before reassigning changed or disconnected numbers.

India

In Rajeswari v. Union of India (decided 30 October 2023), the Supreme Court recorded TRAI's statement that a number deactivated for non-usage, or disconnected at the subscriber's request, isn't given to a new subscriber for at least 90 days. The Court dismissed the petition and said it's up to the earlier subscriber to protect their own privacy, for example by removing their data from apps linked to the old number.

Deactivation itself is covered by separate rules. TRAI's consolidated Telecom Consumers Protection Regulations say a prepaid connection can't be deactivated for non-usage for at least 90 days, with extensions while there's balance left on the account.

What the research found

The best-known study is by Kevin Lee and Arvind Narayanan at Princeton: Security and Privacy Risks of Number Recycling at Mobile Carriers in the United States (APWG eCrime 2021). They sampled 259 numbers that T-Mobile and Verizon offered to new subscribers and checked what those numbers were still connected to.

They also set up 200 recycled numbers as a honeypot. Within a week, nearly 10% received security- or privacy-sensitive messages meant for previous owners, such as authentication codes. When the researchers called customer support to ask about aging periods, they got inconsistent answers. After the study was disclosed, both carriers updated their support pages.

The point isn't that recycling is wrong. Numbers have to be reused. The point is that many people let numbers go while accounts still trust them.

What can go wrong for the previous owner

• Account takeover through SMS reset. If an account lets you reset a password with an SMS code, the new owner of your number may be able to reset it, especially if your email password has also leaked.
• 2FA codes going to a stranger. If SMS is your second factor, the new owner receives your codes. On its own that doesn't give them your password, but it removes one layer.
• Messages and calls. Friends, doctors, schools and businesses that still have your old number will text the new owner.
• Messaging accounts. If you never deleted your messaging account, the new owner may register it on that number. The Supreme Court order notes WhatsApp's practice of removing old account data when an account inactive for 45 days is activated on a different device.

What can go wrong for the new owner

Recycling is annoying for the new owner too: debt-collection calls, a stranger's appointment reminders, and sometimes apps refusing to verify the number because it's already linked to an account. In the US, the FCC Reassigned Numbers Database exists to help callers check whether a number has been reassigned before they call or text it, so the new holder gets fewer calls meant for someone else.

How to protect yourself before you give up a number

1. List every account that uses the number. Banking, email, social media, messaging, shopping, government services, crypto exchanges.
2. Add a non-SMS factor first. Authenticator apps, passkeys or security keys, plus saved backup codes. See our guide to keeping your number for 2FA.
3. Change the number on each account to your new number, then remove the old one, and test that codes arrive.
4. Delete or migrate messaging accounts linked to the old number, rather than leaving them dormant.
5. Tell people. Family, doctors, banks, employers.
6. Only then let the number go.

Numbers you rent online recycle too

This isn't only about SIM cards. Numbers from apps and online providers are also reused when you stop paying or stop using them. Some free app-based services reclaim numbers after a period of inactivity. That's why we say a number used for verification should be one you keep and renew.

At PhoneBorn, phone number plans are real mobile numbers you rent for 1, 3, 6 or 12 months and can renew to keep the same number. If you stop renewing, the number can eventually go to another customer, so move your accounts first. Single-use OTP numbers are different: they receive one code for one service and are meant for sign-ups you won't need to verify again. Don't put an account you care about on one. The glossary entry on number recycling has a short summary, and our VoIP vs mobile checker explains line types.

FAQ

How long before my old number goes to someone else?

In the US, carriers usually hold residential numbers for 45 to 90 days before reassigning them. In India, TRAI told the Supreme Court that a deactivated number isn't reallocated for at least 90 days. Other countries have their own rules.

Can the new owner get into my accounts?

They can if an account still lets someone with the number reset the password or log in by SMS. Princeton's study found many recycled numbers still linked to accounts and leaked credentials. Move your accounts before you give up the number.

Can I get my old number back?

Sometimes, during the holding period, if you contact the carrier quickly. Once it has been reassigned, it's usually gone for good.

Does porting my number count as giving it up?

No. Porting moves the number to a new provider and you keep it. Recycling happens when a number is disconnected rather than ported.

What if I get messages meant for the previous owner?

Ignore codes and don't use them. Reply "wrong number" to people who text you, and update or remove the number from any account that wrongly links it to you.