Thursday, May 30, 2019

How should phone numbers be entered or formatted in ERP and CRM systems?

By Steve Endow

While reviewing the Dynamics 365 Business Central Customer record, I noticed that Business Central allows numbers and symbols, but does not allow any letters in the Phone number field.

This got me thinking...  (ya, I know, dangerous things happen when I think...)

1. How should phone numbers be entered in ERP and CRM systems?

2. How should a system support global phone number formatting?

3. How should a system support phone number extension prefixes (e.g. "x") or notes?

4. How should a system format phone numbers to help support VoIP dialing?

Below are some examples of a few systems to which I have access, and I show how phone numbers can be entered into those systems.

While reviewing how these systems handle phone numbers, I was thinking about my questions above.  I additionally wondered:

What should the minimum length be for phone number fields?  How should users enter phone numbers with extensions?  Should you allow letters in a phone number field?  Should users be able to enter brief notes, like in my examples below?

Initially, I would have thought that restrictions on the phone number values and formats are not required, and users should be able to enter whatever they want / need.  However, if you consider the potential need for VoIP dialing, free form text phone numbers might complicate things.

If you allow any type of text in the phone fields, what issues might that cause if your company uses VoIP dialing?  Can your VoIP dialing software parse a messy phone number value?  Does it need a specific format to support phone extensions? (e.g. semi-colons, pound signs, etc.)

And what about SMS / Text messaging?  If your company wants to offer text message updates to customers, you will likely need to ensure that any Mobile numbers are entered and formatted consistently in order to ensure delivery of text messages.

ITU E.164 - International public telecommunication numbering plan

The International Telecommunications Union has a plan called E.164 that proposes standards for international phone number formatting.  This appears to be the de facto standard for international phone number formatting.

Here is the specification page where you can download the full standrd, and here is a simple overview of the E.164 formatting.

E.164 specifies that the complete phone number have no more than 15 digits, and specifies the format for the different segments of an international phone number

ITU E.164 Number Structure

However, from what I can tell, E.164 does not provide any guidance on phone number extensions, which are fairly common, at least with US businesses.

VoIP Dialer or SIP Formatting Standards

I wasn't able to find any single standard for phone number formatting for VoIP dialing or Session Initiation Protocol (SIP) dialing.  It seems that E.164 is generally recommended for softphone dialing.

This is an interesting article discussing a few of the ways to address SIP number formatting.  It shows an example of how phone extensions might be used for what appears to be internal company extensions, but does not appear to address how one might dial an external phone number with an extension.

My guess is that the more likely situation is that each company will need to research the phone number formatting requirements for their specific internal VoIP dialing software.  Cisco, Polycom, Panasonic, Mitel, and dozens of other VoIP phone systems likely have their own softphones or computer VoIP dialing applications.  And there are dozens of independent desktop VoIP dialing applications, plus apps like Skype and Teams.  So you probably need to determine how those applications want phone numbers formatted to help automated dialing.

And it may be that a single, simple RegEx can clean up whatever value is in a phone number field, and that the specific phone number format entered into a system is not very critical.

Dynamics GP

Here, you can see that Dynamics GP allows entry of numbers, spaces, and symbols in the Phone fields, but by default, it automatically formats the phone number in the North American phone number format.  I don't like the enforced format on the phone fields.

Dynamics GP Phone number fields

Behind the scenes, Dynamics GP stores the phone number values without the North American formatting.

Phone number values are stored in a Char(21) field without the formatting

This design is convenient for companies in the US and Canada with customers and vendors in North America, but not ideal for companies outside North America.  While you can enter a +44 country code, the parens and dash formatting, plus the "Ext." isn't the most user friendly format for an international phone number.  The support for extensions is nice, but what if a customer has extensions with 5 or more digits?

And to my surprise, I can enter any text or note in the Phone fields.  I don't think I had ever tried that before.  But the field length is limited, so notes won't easily fit, and the phone number formatting is applied to the text, making it difficult to read.

It's worth noting that Dynamics GP has 3 Phone fields, plus a Fax field--which seems to be more than most other systems.  However, by default, the phone fields only allow entry of 14 characters, even though the database field is a Char(21).

Dynamics 365 Business Central

Dynamics 365 Business Central has fairly basic Phone fields.  On the Customer Card page, Phone No and Fax No fields are displayed.

The Business Central Phone fields appear to consistently allow up to 30 characters.

Main Customer Phone fields

Interestingly, the main Phone No field allows numbers, symbols, and spaces, but does not allow any letters.  So I cannot type "x9999" for an extension.  I have to skip the extension indicator, or use a symbol, like #.

However, surprisingly, the Fax No field does allow letters.  So I can type anything into that field.

If I edit a Contact Card record, an additional Mobile Phone No field is available.  And while the main Contact Card Phone No field does not allow letters, the Mobile Phone and Fax fields do allow letters.

Business Central Contact Phone fields

I don't know if the choice to prevent letters in the Phone No field was made for a specific reason, but it appears that Mobile and Fax do not have that restriction, which makes me curious why the validation is different or inconsistent between the different fields.

And in an interesting twist, I can enter emojis into the Phone No field.

Letters:  No.   Emojis:  Yes

Microsoft CRM (or whatever it is called these days)

It appears that Microsoft CRM is pretty flexible with its Phone number fields.  This is a sample of an Account record.

Microsoft CRM Account record Phone field

It allows numbers, symbols, spaces, and letters, and supports at least 38 characters based on this test.

I don't have access to MS CRM--a friend provided this screen shot--so I didn't review other record types or test any other phone fields.


The standard NetSuite Customer record has one Phone number field and a Fax field.

NetSuite Customer Phone fields

The Phone and Fax fields allow entry of numbers, symbols, letters, and spaces.

The Phone field allows 22 characters, while the Fax field only allows 21 characters.

A NetSuite Lead record has additional phone fields--Home and Mobile.  The main Phone field allows 22 characters, while the Home, Mobile and Fax fields allow only 21 characters.

NetSuite Lead Phone fields

Zoho CRM

Zoho CRM has plenty of Phone fields on Contact records, and the fields have no entry restrictions.

Zoho CRM Contact record Phone fields 

The main Phone field supports 50 characters, while all of the other phone fields allow 30 characters.

There are no restrictions on the characters that can be entered, so you can use numbers, symbols, spaces, and letters.


I don't really have any specific conclusions at this point, but it was an interesting exercise to consider phone number formatting.

Should an ERP or CRM application restrict the characters that can be entered in a Phone number field?

Should an application attempt to enforce any type of phone number format, like E.164?

Should an application allow letters or notes in Phone fields, like "Ask for Sally"?

My inclination is to allow entry of any characters, and I appreciate the flexibility that larger phone fields offer, such as those that allow over 30 characters.  From what I can tell, formatting a number in the E.164 format shouldn't be too difficult, so my suspicion is that free form text should not pose too much of a challege for VoIP or SIP dialing.

Does your company have specific standards for phone number entry or formatting in your business applications?

Steve Endow is a Microsoft MVP in Los Angeles.  He works with Dynamics GP, Dynamics 365 Business Central, SQL Server, .NET, Microsoft Flow, and PowerApps.

You can also find him on Twitter and YouTube

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