TL;DR
- Text PAC to 65075 to receive your PAC code instantly; your current provider must supply it within a few seconds by text and confirm it in writing.
- Under Ofcom rules, once your new provider submits the PAC code, porting must complete by the end of the next working day.
- Your old SIM stops working at the point the port completes, typically mid-morning on the transfer day.
- A brief overlap period exists: you can still use your old SIM up until the moment of cut-over.
- If porting fails or is delayed, your new provider is responsible for resolving the issue with your old network.
What a PAC Code Is and Why It Exists
A Porting Authorisation Code (PAC) is a unique nine-character alphanumeric code that authorises the transfer of your mobile number from one UK network to another. Ofcom introduced mandatory PAC-based number porting to ensure consumers can switch networks without losing their number, removing a significant barrier to competition in the retail mobile market.
The PAC system is governed by General Condition C8 of Ofcom's General Conditions of Entitlement, which places binding obligations on all UK mobile operators. Without a PAC code, your number belongs to your current network and cannot be moved. The code is personal to your account and expires after 30 days if unused, after which you would need to request a new one.
How to Request Your PAC Code
Since July 2019, the fastest and most straightforward method is to text the word PAC to 65075. This free service, operated across all major UK networks in compliance with Ofcom requirements, returns your PAC code by text message within seconds. The message also includes information about any outstanding contract charges or early termination fees you may owe, giving you a complete picture before you commit to switching.
Alternatively, you can request your PAC by calling your current provider's customer services or via their website or app if offered. Providers are required under Ofcom rules to supply the code immediately when requested by text, or within two hours if requested by other means during business hours. They are prohibited from making the process difficult or from using the request as an opportunity to pressure you into staying.
The Porting Timeline: Stage by Stage
Once you have your PAC code, you give it to your new provider alongside an agreed switch date. Your new provider then submits the PAC electronically to your old network through an industry system managed by the Port Management Company. Ofcom rules require the actual number transfer to complete by 11:59 pm on the next working day after the PAC is submitted, although in practice most major networks complete porting by mid-morning of that working day.
The timeline begins when your new provider formally submits the PAC, not when you hand the code over to them. If you provide the PAC on a Friday evening, your new provider may not submit it until Monday morning, and the one working day clock starts from submission rather than receipt. It is worth confirming the expected transfer date with your new provider so you are not caught out over a weekend or bank holiday.
| Stage | Action | Ofcom Time Limit | Typical Experience |
|---|---|---|---|
| 1. PAC Request | Text PAC to 65075 or call provider | Immediate (text) / 2 hours (other methods) | Seconds by text |
| 2. PAC Submission | New provider submits code to old network | No mandated window; agree date with provider | Same or next business day |
| 3. Port Processing | Networks exchange data; number reallocated | By end of next working day after submission | Mid-morning on transfer day |
| 4. Old SIM deactivates | Old network removes number from account | At point of port completion | Simultaneous with new SIM activation |
| 5. New SIM active | Number live on new network; calls and data work | Immediate on completion | Within minutes of cut-over |
What Happens to Your Old SIM
Your old SIM card continues to work right up until the moment the port completes. During the period between requesting your PAC and the actual transfer, you remain a customer of your old network on the same tariff and conditions. Calls, texts, and data all function normally. There is no need to keep a second phone running or manage two numbers simultaneously during this window.
At the point of cut-over, your old SIM is deactivated automatically. You will typically notice this as the handset losing signal or displaying a 'no service' or 'SIM not provisioned' message. This is normal and expected. You should have your new SIM inserted and ready to go, as the new number becomes active on the new network within minutes of the old SIM losing service. Inserting the new SIM and toggling Airplane mode off usually prompts the handset to register on the new network immediately.
The Brief Overlap Period and What You Can Do
Between the moment you hand your PAC to your new provider and the transfer date, both SIMs are technically valid in the sense that your old account remains open. This overlap is intentional and consumer-protective: you are not cut off before the new service is confirmed. You can continue to use your old SIM for calls and data right through to the morning of the transfer, and there is no requirement to stop using it early.
It is worth being aware that during this overlap period your old provider may still bill you for usage in the usual way. If you are on a pay-monthly plan, you will typically receive a final bill for the days up to and including the port date, calculated on a pro-rata basis. Your new provider's billing starts from the day the port completes. Checking both bills carefully after switching is advisable to avoid paying for the same period twice.
What Ofcom Rules Say About Delays and Failures
Ofcom's General Condition C8 places clear responsibilities on both the losing and gaining networks. If a port does not complete within the mandated one working day window, your new provider is required to investigate and resolve the failure as a matter of priority. Common causes of delayed ports include mismatched account details (for instance, the account holder name submitted does not match the old network's records), system outages, or a PAC code that has expired.
If you experience a delayed port, contact your new provider first, as they are the responsible party for progressing the transfer. Ofcom's guidance notes that consumers should not have to liaise directly with their old network to resolve porting failures - that co-ordination is the gaining operator's responsibility. If delays are prolonged or you suffer material detriment (such as being without mobile service for an extended period), you can raise a formal complaint and, if unresolved within eight weeks, escalate to an Alternative Dispute Resolution scheme approved by Ofcom.
What this means in practice
Sarah, a teacher in Birmingham, decides to move from her current network to a new SIM-only deal on a Tuesday afternoon. She texts PAC to 65075 and receives her nine-character code within seconds, along with a note that she has no outstanding contract balance. She shares the PAC with her new provider that evening. The new provider submits the code on Wednesday morning. By 10:30 am on Thursday her old SIM shows no service; she inserts her new SIM, switches Airplane mode on and off, and within two minutes her number is live on the new network. Her old provider issues a pro-rata final bill covering the two days of her billing period before the port date, and her new provider's first bill starts from Thursday.
Related Guides
How we verified this
This article draws on Ofcom's General Conditions of Entitlement (General Condition C8), the Ofcom Switching and Porting guidance pages, and the Ofcom-mandated text-to-switch service documentation published at ofcom.org.uk. No operator-specific pricing or proprietary data has been used.
Disclaimer: Kaeltripton.com is an independent UK editorial publisher. We are not regulated by Ofcom or the FCA and we do not sell or arrange mobile services, insurance, or financial products. This content is for general information only and is not legal, financial, or technical advice. Rules, prices, and operator policies change. Verify the current position with Ofcom, GOV.UK, the ICO, or your provider before acting. ICO registered ZC135439. Last reviewed: 2026-06-05.
Frequently Asked Questions
How long does a PAC code transfer take?
Under Ofcom's General Condition C8, once your new provider submits your PAC code to your old network, the number must port by the end of the next working day. In practice, most major UK networks complete the transfer by mid-morning on the working day following submission, meaning the entire process from PAC request to live number typically takes two to three working days from start to finish.
When does my old SIM stop working after a PAC transfer?
Your old SIM is deactivated at the precise moment the port completes, which is typically mid-morning on the agreed transfer day. Up until that point your old SIM continues to function normally for calls, texts, and data. The deactivation is automatic and simultaneous with your number becoming active on the new network, so there is no intentional gap in service.
What if my number has not ported after the expected time?
Contact your new provider immediately, as they are responsible under Ofcom rules for progressing the transfer and liaising with your old network. Common causes include mismatched account details or an expired PAC code. If the delay causes material detriment and is not resolved promptly, you can raise a formal complaint with your new provider and, after eight weeks without resolution, escalate to an Ofcom-approved Alternative Dispute Resolution scheme.
Can I use my old SIM while waiting for the port?
Yes. From the moment you request your PAC through to the instant the port completes, your old SIM remains fully active. There is no requirement to stop using it. You will continue to be charged by your old provider for any usage during this period in the normal way, and you should expect a pro-rata final bill covering the days up to and including the port date.
Is there any service interruption during porting?
There is typically a very brief interruption of a few minutes at the exact moment of cut-over, when your old SIM loses service and your new SIM registers on its network. This is normal. Having your new SIM already inserted in your handset and toggling Airplane mode off as soon as the old SIM shows no signal usually brings the new service live within two to five minutes. Prolonged outages lasting hours are not expected and should be reported to your new provider.
