Step 1 - Validate on capture
Start at the source: when a customer enters their number (or when it enters your systems).
- Normalise the format (store in E.164, e.g. +447..., so everything is consistent)
- Detect country (so you can apply the right rules for length/prefixes)
- Flag obvious invalid numbers (wrong length, impossible patterns, missing country code, etc.)
Step 2 - Enrich the record
Once the number is structurally sound, add the context that helps you route and make decisions.
- Line type (mobile, landline, or internet-based/VoIP)
- Carrier and porting context (which network currently serves the number, and whether it’s moved networks)
- Risk flags where appropriate (e.g. signals that suggest low trust or higher fraud likelihood)
Step 3 - Decide what to do
Validation is only valuable if it changes what happens next. Build simple rules your teams can agree on:
- Invalid format? Ask for a correction immediately.
- Landline provided for OTP? Prompt for a mobile number or offer a fallback channel.
- High-risk signals? Use step-up verification, throttle, or route to review.
- Unknown signals? Allow the record through, but monitor outcomes (delivery, complaints, conversion).
Step 4 - Keep it clean
Validation isn’t “one and done”, contact data decays over time.
- Revalidate key segments on a schedule (new customers, dormant customers, high-value cohorts)
- Validate before major sends (campaigns, service notifications, billing runs)
- Monitor failure rates by country, source, and channel; spikes often indicate upstream data issues or routing/provider problems
Common mistakes (and how to avoid them)
Mistake 1: Treating “valid format” as “deliverable”
Fix: use multiple signals, especially for OTPs and time-critical messages.
Mistake 2: Storing numbers inconsistently
Fix: standardise storage (e164) and enforce it at the point of capture.
Mistake 3: Applying harsh rules without considering conversion
Fix: use step-up verification for unknown cases rather than blanket blocking.
Mistake 4: Cleaning once and assuming you’re done
Fix: validate continuously, data decay is real.
The quickest win
If you want fast impact:
1. Validate at the point of capture,
2. Normalise to a single stored format (e164),
3. Add line type and porting-aware intelligence,
4. Use those outputs to improve routing and reduce failures.
Alternatively, let Acudo take care of your number validation for you.
If you want help choosing the right depth of validation (and how to apply it across onboarding, fraud prevention, and high-volume messaging), talk to the Acudo team.