Phone number formats in Europe

Half the problems with a phone list are not about the people on it but about how the numbers are written. One wrong zero and a sending tool rejects the number — or, worse, sends to someone else.

The international format: E.164

Sending platforms expect numbers in E.164, the international standard: a plus sign, the country code, then the national number without the leading 0 ("trunk prefix") that people dial at home. No spaces, no dashes, no brackets, and never more than 15 digits in total. A UK mobile written 07700 900123 at home becomes +447700900123.

Mobile formats in our six countries

Spaces in the table are only for reading — the file should have none.

The mistakes we see most

• Keeping the 0: +4407700… or +3106… are invalid. Drop the 0 after the country code.
• Italy is the exception: Italian landlines keep their 0 after +39 (Rome is +39 06…), mobiles have none. Do not "fix" one rule onto the other.
• Spreadsheets eating numbers: open a list in Excel and +447700900123 can turn into 4.477E+11, losing the plus and digits. Import the column as Text, or open the TXT file in a text editor instead.
• Mixed formats: the same number written twice — once +31 6…, once 06… — slips past duplicate checks. Normalise first, then de-duplicate.
• Austria's variable length: Austrian mobile numbers are not all the same length, so a "fixed length" filter will throw away good numbers.

Cleaning a list in four steps

1. Remove everything that is not a digit or a leading plus.
2. Add the country code where it is missing, removing the national 0.
3. Check the result starts with the right country code and mobile prefix (+447, +316, +393, +3519, +436; Danish mobiles start with several digits, so check the length: 8 after +45).
4. Remove duplicates — and remove everyone on your opt-out list.

Storing numbers in your own systems

Keep every number in your CRM or database as text, in E.164, never as a numeric field — a number type drops the plus and can round long values. Store the country in its own column so you can filter and apply the right rules per market, and keep the "pretty" format with spaces only for display. When you import a new list, normalise it first and check it against what you already have, so the same person is never messaged twice from two lists.

How our files come

Every list is delivered as a TXT file, one number per line in international format (+447…, +316…, +4520…), ready for any sending tool — CSV on request. No cleaning needed; just keep it away from spreadsheets that reformat numbers.