Last Updated: 31st May 2024


• Number Porting is always led by the Gaining Communications Provider (GCP)
• Number Portability exists for end-users wishing to change retailer (The current billing provider.)
• Number Porting is a best endeavour process.


What is Number Porting
What happens when my telephone number ports?
How do I import a telephone number into the ACS Business network?
What can cause porting delays?
Pre-Order Validation PoV
How do I export a telephone number from the ACS Business network?
The Export Process
Telephone Line Type definitions
Documents Required for Porting
Minimum Lead Times
Single Line Geographic Port Procedure
Multi Line Geographic Port Procedure
Non-Geographic Line Port Procedure
Port Override Requests
Rejections – Why has my number port been rejected?
Public Directory Entries


ACS Business will always endeavour to port your inbound telephone numbers to the ACS Business VoIP service in a timely fashion. However, we cannot provide any guarantees that numbers can port successfully or at all, that numbers can port within a certain timeframe (including but not limited to the minimum industry lead time for the import type), or that there will not be problems porting the number(s) away from your current provider.

Please note that whilst UK number portability is regulated by the UK Telecommunications Regulator (Ofcom) in line with UK regulations, UK geographic and non-geographic number porting is presently a best-endeavours process with no guarantees, and all lead times quoted in this article are minimum industry standards.

The accepted practice is for service providers who have been allocated numbers from Ofcom to have completed the technical service establishment and signed a porting agreement with at least 1 network operator to be able to export their allocated numbers, however this is not a mandatory requirement when taking allocations of telephone numbers from the UK telecommunications regulator (presently Ofcom).

Reseller or Wholesale porting from one service provider to another service provider is not supported, as number portability exists for subscribers/end-users wishing to change provider only. This applies to any imports to ACS Business and exports from ACS Business.

Any number port orders received to import or export numbers via ACS Business which are suspected of being reseller ports will be rejected, however, changes in service type (e.g. ISDN to Hosted PBX) may be permitted on a case by case basis.

Number porting may incur charges from any intermediary parties (including the current provider and/or your new provider) facilitating your port orders, please be aware of this before committing to submit a port order. Additionally, please be advised that amending the port date may not be possible depending on the type of circuit or number due to port.

What is Number Porting

Number porting is a change in the CP (Communications Provider) or Current Network Operator (CNO) of the inbound routing of a telephone number.

UK number porting is made technically possible by onward routing, where the number(s) to be ported are prefixed by the rangeholder or host network operator for the rangeholder with a number porting prefix for the gaining network operator. When a call is placed to the ported number after the porting prefix has been applied the call is then routed directly to the gaining network operator via the designated points of interconnect agreed under the service establishment between the new network operator and the host network or rangeholder.

As such number porting does not change the Ofcom-allocated RH (Range Holder) of a number, as the calls will usually always route through the RH systems or the RH’s host network operator.

ACS Business use BTIPEX (BT IP Exchange) for most porting requests for the ACS Business platform. IPEX has arguably the widest SE (Service Establishment) with range holders and host networks, enabling ACS Business to facilitate the porting of most UK landline and non-geographic telephone numbers, particularly from the larger tier 1 network operators.

IPEX cannot import a number from a RH or host network that they do not have service establishment (SE) with. In any case, where IPEX do not have SE with a range holder or host network, they will attempt to complete SE with them and sign a porting agreement for the portability of those numbers. The SE process can take a minimum of 55 working days for geographic numbers, however, any errors or obstructions found on the systems they are attempting to service establish will lengthen this timeframe accordingly, in addition, a porting agreement must be signed before porting orders may be exchanged.

For a port request to be accepted by the CNO (Current Network Operator) / Losing CP (LCP) or RH, all the information on the documents forwarded to the LCP/RH must match what is on file for the telephone number(s) to be ported. It is usually best to contact the current provider and ask them what is on file for the postcode and additional information against the numbers to be ported when filling out the porting document, at this point you may also inform them of your intention to port the number away from them, so that the port request is not obstructed.

ACS Business can attempt to facilitate direct porting agreements and service establishments with network operators that fall out of scope with the BT standard interconnect agreement. Our porting team will be able to advise you should this situation arise.

What happens when my telephone number ports?

When a number ports from a fixed telephone line, the original line is usually ceased. This means that all additional services directly provided on the telephone line will also be ceased, e.g broadband or voicemail. Number port prefixing on analogue and digital line (ISDN) import activations from BT as the range holder usually happens at the exchange level.

When a number is ported to our service, the original RH changes the prefix on the number, so that it routes out to IPEX. It is imported onto the IPEX platform and programmed in their core routing engine, which then routes all calls into that number onwards to the ACS Business platform.

How do I import a telephone number into the ACS Business network?

For ACS Business to port your number onto the ACS Business VoIP platform, we need, for all numbers:

  • Proof of ownership of the number (ideally in the form of a copy of the latest bill from the current CP)
  • Authorisation from the subscriber to port the number (in the form of a GNP Customer Letter of Authority signed by the subscriber)
  • Relevant telephone number details (in the form of completed porting documents)
  • Range holder CUPID (find on AND check against Ofcom S1 allocation form)
  • LCP CUPID (may also be Range holder, otherwise is the company billing you for the number)

We are unable to progress any ports without this information.

What can cause porting delays?

There are several factors that can delay port orders:

  • Redcare / security tag exists on the line. You must cancel Redcare or transfer the service to another circuit number before that number can be ported.
  • The Installation address or postcode is incorrect or does not match the current network operator’s data against the number. We need to know the current postcode of the number(s) for a port order to validate correctly. See Pre-Order Validation PoV
  • LCP/RH failure to provide a response. You should always inform the current provider of an intention to port away so that a port order is not held up.
  • No SE (Service Establishment) with LCP/RH. Unfortunately, you as the subscriber can do nothing to affect this.
  • Incorrectly labelled (single line as multiline etc). You should always confirm the line type with the LCP/RH.
  • Incorrect telephone details (main billing number, DDI range etc). You should always confirm with the LCP/RH all attached phone numbers, main billing number etc).

Pre-Order Validation PoV

ACS Business can request the line information (associated address) held by a CP/NO that is UK registered on the Ofcom scheme. This mitigates the trial/error of porting numbers with unknown details.

The Ofcom register is available here:

How do I export a telephone number from the ACS Business network?

The number porting process is always GCP (Gaining Communications Provider) led and exists exclusively for the end-user/subscriber. This means that to export numbers, the subscriber follows the import process with another provider. The LCP simply validates the data submitted accordingly. A Customer Letter of Authority (CLoA) is still required with the new provider, and this is checked prior to exports being progressed. Porting guidelines are industry-wide so the process will usually be like another CP.

It is always expeditious to provide ACS Business with a copy of the CLoA if your porting timescale is short as delays in receiving this from the GCP will cause the port to time-out as it cannot be validated.

Any number that has been ported into ACS Business, can usually be ported out again, i.e where we are not the range holder. Numbers imported to ACS Business can usually be exported as they were initially imported, or split accordingly, however, if numbers to be ported where a range of numbers was imported then that entire range must be exported to keep the desired number(s).

Non-Geographic number ranges (beginning 03, 05, 08 or 09) carry restrictive porting measures and are not covered by regulations.

Numbers that are not in service cannot be exported. The number(s) to be ported must be live and be working to be ported. Any number ports requested for numbers that fail when calling will be rejected.

Reseller / Wholesale bulk porting of subscribers’ numbers into or out of ACS Business is not supported as number portability exists for subscribers (i.e. end-users) wishing to change provider only. Any reseller ports requested will be rejected. The above process is mandatory in all circumstances.

The Export Process:

  • Submit your GNP request to the GNP.
  • ACS Business will be notified by BT Openreach of the export request.
  • ACS Business will validate the request and notify the subscriber/reseller for legitimacy.
  • Legitimate requests are then cleared for export subject to lead times.

Telephone Line Type definitions

  • Single Line Geographic – A single telephone number beginning 01 or 02, that is not part of a DDI range, is not the main billing number for a DDI range and is not part of a multi-line.
  • Multi Line Geographic – Multiple lines on one or more telephone numbers, including WLR analogue Multi-Line and single-number ISDN.
  • Simple DDI – Multiple digital lines (ISDN/T1/E1/SS7) on one or more telephone numbers, consisting of a main billing number. It can contain a whole block of DDI’s (minimum 10, multiple of 10) and/or have SNDDIs on the circuit.
  • Complex DDI – Multiple digital lines (ISDN/T1/E1/SS7), consisting of part of a block of DDI’s, and a main billing number. Note: All DDI’s attached to the circuit must be included on porting document, and intention given as to which numbers to port. Any numbers not ported will be handed back to the RH.
  • Single Line Non-Geographic – A single telephone number that is non-geographic, is not part of a DDI range, is not the main billing number for a DDI range and is not part of a multi-line or Feature Line.
  • Multi Line Non-Geographic – Multiple non-geographic telephone numbers, consisting of an original and whole block of DDI’s (minimum 10), and a main billing number.
  • International – Telephone numbers from countries outside the UK (+44).

Documents Required for Porting

  • Single Line Geographic – Porting Form, Letter of Authority, Copy of Latest Bill
  • Multi Line Geographic – Porting Form, Letter of Authority, Copy of Latest Bill
  • Simple & Complex DDI – Porting Form, Letter of Authority, Copy of Latest Bill
  • Non Geographic – Porting of Non-Geographic Numbers Notice, Copy of Latest Bill
  • Multi Line Non Geographic – Porting of Non-Geographic Numbers Notice, Copy of Latest Bill
  • International – Requirements vary and are country specific

Minimum Lead Times

  • Single Line Geographic Import – 4 to 13 working days
  • Multi Line Geographic Import – 7 to 25 working days
  • Simple DDI – 10 to 23 working days
  • Complex DDI – 22 to 25 working days
  • Non-Geographic Import – 15+ working days
  • International (non-uk) – Varies between countries

Single Line Geographic Port Procedure

  1. Customer submits to ACS Business: Porting form (Customer Letter of Authority / CLoA), copy of the latest bill.
  2. ACS Business submits to IPEX using online portal with CRD (Customer Required Date).
  3. IPEX complete an automated look up on their systems, verifying line type and range holder.
  4. If details match records with LCP/RH, the order is confirmed.
  5. IPEX receive response from LCP/RH confirming acceptance on DD/MM/YYYY@HH:MM
  6. ACS Business notifies the customer that number has been accepted to port.
  7. At least 24 hours prior to port, ACS Business will add the porting number to the customer’s account ready to receive traffic from BT IP Exchange.
  8. On date and time of port, IP Exchange automatically loads number onto ENUM and direct calls from that number to ACS Business so they are ready to catch traffic from RH.
  9. RH automatically applies porting prefix, so calls are routed.
  10. Confirmation that number has ported is sent by IP Exchange to us.
  11. ACS Business test-call after receiving completed port notification to make sure calls are routing correctly. If not routing correctly, escalate to BT immediately.

Multi Line Geographic Port Procedure

  1. Customer submits to ACS Business: Porting form, Letter of Authority, copy of the latest bill.
  2. ACS Business submits a request to IPEX using online portal.
  3. IPEX then apply this information on a NPOR form manually.
  4. NPOR gets sent to BT Openreach, who send it off to the LCP/RH.
  5. LCP/RH then check the details on the NPOR and respond back to Openreach accordingly, if rejected providing the reason why.
  6. Openreach then sends the response to IPEX.
  7. If accepted, a confirmation response is sent to ACS Business confirming date and time the porting process will begin.
  8. At least 24 hours prior to the port, ACS Business add numbers into customer’s account ready to receive traffic.
  9. On the date of port, ACS Business manually configures the number port on IP Exchange portal after the Port Configuration Window Start(s). This loads it into ENUM.
  10. On date and time of port, ACS Business call IP Exchange, give reference number(s) and/or MBN, and ask them to progress the port and perform a test-call to make sure ENUM load is correct.
  11. Openreach then progresses the port, where the RH applies the porting prefix, and inbound traffic on PSTN should then route through to ACS Business.
  12. If there is downtime of 15 minutes or more ACS Business ring IP Exchange requesting they escalate due to the downtime.

Non-Geographic Line Port Procedure

  1. The subscriber has to fill in a separate Non-Geographic Number Porting Notice – this form must be typed, printed on customer-headed paper, signed and dated and sent back to us with a copy of a bill from LCP. There must be an account number the subscriber has with the current provider where available, the address of the Losing Communications Provider and contact email address and telephone number, and the Gaining Communications Provider must be ACS Business Ltd and our address.
  2. If resellers are involved in the transaction the porting lead-time stretches – for non-geographic porting, all parties must be informed of the port request. The minimum lead time for non-geographic number porting is 15 working days.
  3. Once all the correct subscriber paperwork is received, ACS Business sends the paperwork to IPEX, who then process the port request on ACS Business’s behalf via BT Inbound Services. Inbound Services then send a port request to the current communications provider (this could be a reseller) or reject the port request because of incorrect paperwork or inability to port.
  4. BT, upon acknowledgement of the porting request to the end-users provider, then approach the RH with a port order.
  5. Once the port order has been accepted, a confirmed date for the port to take place will be confirmed to IPEX, and if appropriate a fixed time or time range.
  6. At least 24 hours prior to the port taking place, ACS Business will add the number(s) required into the subscriber’s ACS Business account ready to receive inbound calls,
  7. On the date and time of the port, IP Exchange builds the number(s) on ENUM, then contact RH to initiate porting prefix.
  8. The number should then have been ported, ACS Business does test calls to confirm number routes to us correctly. If there is downtime of 15 minutes or more ACS Business ring IP Exchange requesting they escalate due to the downtime.

Port Override Requests

POR (Port Override Requests) exist to force through a number porting request when the LCP is deliberately blocking or being obstructive towards the end users right to retain the telephone number.

POR (Port Override Requests) can be placed on any UK originating line type be it Geographic, Non-Geographic, Residential or Business, Single or Multiline.

The decision to initiate the POR process must be a joint decision made by the End User’s Retailer (i.e. the Gaining Party-GP) and the Gaining Wholesaler (i.e. the Gaining CP-GCP), on the basis that both parties will have first hand knowledge of the port order in question and the obstacles preventing it’s progress.

POR (Port Override Requests) have a 6-stage process.

  1. Stage 1 – POR alert
  2. Stage 2 – POR trigger
  3. Stage 3 – POR Evidence Pack
  4. Stage 4 – POR Pack submitted for EAP approval.
  5. Stage 5 – POR Executive Authorisation Panel (EAP)
  6. Stage 6 – POR execution & closure

Rejections – Why has my number port been rejected?

Most common number Port rejection reasons can be avoided by completing a PoV (See above)

Here are some of the common rejection codes and their reasons and explanations.

  • Code 2 = CUPID missing or invalid
    • Code 6 = Porting telephone number missing or invalid
    • Code 15 = Other (must detail reason for rejection separately)
    • Code 25 = Single Line Order but porting telephone number is Multi Line
    • Code 26 = Multi Line Order but porting telephone number is Single Line
    • Code 30 = Telephone Number Already Ported
    • Code 31 = Customer has no service with LCP
    • Code 32 = Porting request out of current scope for Number Portability
    • Code 41 = LCP Installation Postcode invalid

Public Directory Entries

Special Phonebook entries (SPBE) carry charges and if the number(s) being imported are active within Directory Management Solutions (i.e. the BT Phonebook or Directory Enquiries), you may be notified of charges without prior notice when a reprint occurs.

Any unwanted directory services must be cancelled as soon as possible with the current service provider to avoid unwanted costs.


In the context of this document, the following acronyms are used:

  • IPEX = British Telecom IP Exchange
  • IPEX = IP Exchange
  • CUPID = Communications Unique Provider ID
  • CP = Communications Provider
  • LCP = Losing Communications Provider
  • CNO = Current Network Operator
  • GNP = Geographic Number Porting
  • CRD = Customer Required Date
  • RH = Range holder
  • SE = Service Establishment
  • DDI = Direct Dial In
  • ISDN = Integrated Services Digital Network (ISDN2e or BRI, ISDN30e or PRI)
  • PSTN = Public Switched Telephone Network
  • SS7 = Switched Signalling 7 – a set of protocols typically on a fixed E1 circuit defining call routing and signalling
  • NGN = Non-Geographic Number
  • ENUM = E.164 Number Mapping – IPEX’s call routing engine which directs incoming calls on telephone numbers to the allocated carriers/destinations
  • Code 44 = Telephone number(s) associated with MBN missing or invalid
  • Code 52 = Invalid Range Holder (i.e. telephone number does not belong to Range Holder)