Phone numbers look like the simplest field in a CRM, and that is why nobody agrees on how to write them. One colleague types 06-12345678, another +31 6 1234 5678, a third copies a number from an email signature including "(0)" and a few dots. Each version is readable for a human, but for the CRM they are different strings. Pomio CRM recommends one international format for every number, because it costs a minute to agree and saves hours of searching, merging and misdialling later.
Why the format matters
Search. A customer calls from a number you do not recognise. If numbers are stored in one format, a single search finds the contact. If they are stored in five formats, you only find them when you happen to type the same spaces and dashes.
Duplicates. A phone number is one of the best signals that two records are the same person or company. That only works if the numbers are written the same way; see checking imports for duplicates first and who may merge duplicate records.
Calling and integrations. Click-to-call, telephony integrations and messaging tools expect a number they can dial from anywhere. A national number with a leading 0 is wrong as soon as the caller or the customer is in another country.
Which format to choose
Use the international notation: a plus sign, the country code and the national number without the leading 0, written without spaces, brackets or dashes. A Dutch landline 020-1234567 becomes +31201234567, a Dutch mobile 06-12345678 becomes +31612345678 and a German number 030 1234567 becomes +49301234567. Avoid the "+31 (0)20" style: it mixes two notations and is often dialled incorrectly.
Some teams prefer spaces for readability, such as +31 20 123 4567. That can work if everyone follows exactly the same pattern, but a format without spaces is easier to search, compare and export. Pick one and write it down.
Separate fields, not one box
Mobile and landline apart. Use separate fields for a direct mobile number and a general or landline number, so nobody has to guess which one reaches the person.
No notes in the number field. Extensions, "ask for reception" or "only mornings" belong in a note or a separate field, not after the number, because text in the field breaks search and dialling.
Company and contact. A general switchboard number belongs on the company; a personal number belongs on the contact. Linking contacts to companies keeps both reachable; see linking every contact to a company.
Fix it at the door: imports
Most messy numbers come in through imports: event lists, exports from an old system, spreadsheets from a colleague. Convert the phone column to the agreed format in the spreadsheet before you import, and use the clean numbers in the duplicate check. The same applies when data leaves the CRM: a consistent format makes an export to CSV usable in other tools without another clean-up.
Keep it clean: the monthly check
Add one line to your monthly data quality check: numbers that do not start with a plus sign, numbers containing letters or spaces, and the same number on several records. Fix them while the list is still short.
Privacy: store what you need
A business phone number of a contact person is personal data under the GDPR. Store the numbers you need for the relationship, remove personal numbers when someone leaves the customer, and do not copy private numbers from social media into the CRM without a reason.
In short
Store every phone number in one international format with a plus sign and country code, without spaces, a leading 0 or notes; keep mobile and landline in separate fields; convert numbers during import; and check the format monthly.