Phony Phones and Real Numbers

There are plenty of data quality issues related to phone numbers in party master data. Despite that a phone number should be far less fuzzy than names and addresses I have spend lots of time having fun with these calling digits.

Challenges includes:

  • Completeness – Missing values
  • Precision – Inclusion of country codes, area codes, extensions
  • Reliability – Real world alignment, pseudo numbers: 1234.., 555…
  • Timeliness – Outdated and converted numbers
  • Conformity – Formatting of numbers
  • Uniqueness – Handling shared numbers and multiple numbers per party entity

You may work with improving phone number quality with these approaches:


Here you establish some basic ideas about the quality of a current population of phone numbers. You may look at:

  • Count of filled values
  • Minimum and maximum lengths
  • Represented formats – best inspected per country if international data
  • Minimum and maximum values – highlighting invalid numbers


National number plans can be used as a basis for next level check of reliability – both in batch cleansing of a current population and for an upstream prevention with new entries. Here numbers not conforming to valid lengths and ranges can be marked.

Also you may make some classification telling about if it is a fixed net number or cell number – but boundaries are not totally clear in many cases.

In many countries a fixed net number includes an area code telling about place.

Match and enrichment:

Names and addresses related to missing and invalid phone numbers may be matched with phone books and other directories having phone numbers and thereby enriching your data and improving completeness.

Reality check:

Then you of course may call the number and confirm whether you are reaching the right person (or organization). I have though never been involved in such an activity or been called by someone only asking if I am who I am.

6 thoughts on “Phony Phones and Real Numbers

  1. Per Olsson 8th December 2009 / 06:03

    The secret would be to do offer phone number validation depending on users origin but then theres the problem that he could have lied ot keyed in wrong info, in a online point of view.

    Interesting post, I think information validation will be a bigger and bigger issue the more data we will have in our systems around the world but with high data quality from the beginning it could be easier and easier to validate

  2. wesharp 8th December 2009 / 16:18

    Two things that struck me as I read the post was the use of reference data (aka the white/yellow pages in the US) and the issue surrounding uniqueness of phone numbers.
    Business users tend to think of phone numbers as more unique than they truely are and depend on this information far too much.
    Now the issue of using public directories as phone reference data is an interesting method!
    Thanks, as usual, for your perspective on external reference!

  3. Henrik Liliendahl Sørensen 8th December 2009 / 16:50

    Thanks Per and William (wesharp)

    I agree Per, the more you can solve upstream the better. It is though not absolutely necessary to catch every single data element you may think of – just having sufficient raw data that makes you able to obtain these data in a current state in an easy matter at a later point could be more powerful.

    William, I also agree with you on the risk in looking at phone numbers as unique identifiers. Mostly you have to combine with names, addresses and other ID’s to get there – and then beware of merging the 2 rows with “John Smith” having phony number 5555555555.

  4. PaulBoal 8th December 2009 / 18:02

    I haven’t been called just to find out who I am, but I’ve certainly had that as an explicit part of a call. Every year the university I attende calls to ask for donations, and explicitly verifies all of my contact information. That seems like a good practice to be in the habit of, if you have other reasons to reach out to contacts anyway.

  5. Vish Agashe 8th December 2009 / 20:37


    As usual nice post.

    I wonder if you or others have now implemented compliance validation as a part of data validity. For example, you might want to check all valid phone numbers against do not call list and make sure you identify that on the customer record (at least in the US). I am sure every country might have some regulations around how phone numbers can be used by Vendors.

    Also in early 90’s banks actually called the numbers and validated if phone number is valid or not using telephony (I guess that was best way to validate if number of was valid)…. and the telephony solution worked really well.

    Vish Agashe

  6. wesharp 8th December 2009 / 20:44

    the telephony solution is an interesting one, Vish.
    you guys can really get me thinking!

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