Number Porting

This information is to help with any questions relating to the porting of telephone numbers

Number porting is the process of moving a telephone

number from one provider to another. It sounds simple

but in the real world things are never that easy.


If you want to move to the new world of internet telephony then you may want to keep your

old phone numbers. To do this you need a number port.

Number porting is the process of moving a telephone number from one provider to another.

It sounds simple but in the real world things are never that easy.


You will be asked to fill in a form called a GNP form and submit it to us by email. It’s vital the

details on the form are correct to prevent a number port being rejected.

As well as this you may also be asked to provide a recent phone bill as proof of ownership.


Numbers can be ported from all sorts of lines. The simplest is a single line port where a line

has one number assigned to it. However, numbers on other types of lines such as ISDN2

and ISDN30 can also be ported. With ISDN there is a range of numbers on any line called

DDI’s. These all need to be ported. You cannot pick and choose.


Every standard telephone (PSTN) line needs a number assigned to it for it to work. If a

number leaves a line during the porting process the line that it has left will cease.

Phone lines are not just used for phone calls any more. They often carry broadband

amongst other things. If the number leaves a line, the line will cease leaving you without


RedCare is a process whereby a constant signal is sent down the line and is then monitored

for breaks in the signal. It is used in burglar alarms and panic buttons etc. If a line has

RedCare on it the number for that line will not be able to be ported until RedCare has been

removed. VoIP systems do not in general provide a good replacement for Red Care.


You need to be careful that you don’t cease the line on which your chosen number sits prior

to the number port because that terminates the number and it then enters “quarantine”

where it cannot be used by someone else or you.  It also means that it cannot be ported. So

ceasing a line and then deciding to port the number just doesn’t work.


Number ports get rejected for all sorts of reasons. If the details given on the GNP form are

not correct the port will fail. One of the most common reasons is an incorrect postcode. The

postcode that the number is registered to needs to match that on the form. When numbers

have been previously ported and/or the business has previously moved the situation can be

a problem.

It is always worth ringing your old provider to make sure you have the right postcode before

submitting the GNP form. Resubmissions cost time and money.


How long it takes to port a number will depend on the complexity and type of line the number

is on. The guidelines are as follows:

• Single analogue line request 10 working days

• Up to 10 lines single analogue lines 21 working days

• Multi Line - 10 lines or less 14 working days

• Multi Line - 11 or greater (or a Centrex site) 24 working days

• Simple DDI 24 working days

• Complex DDI 30 working days

• ISDN 10 lines or less 14 working days

• ISDN 11 lines or more 30 working days

The times can vary significantly.


Once you’ve submitted a port request and it has been accepted you will be given a date

when the port will complete. You need to ensure that your hardware is up and running in

advance of this, so that your phone service carries on seamlessly. Our engineers will pay

particular attention to this process making sure that your new phones work in advance.