Why lists go bad
Numbers change hands constantly. People switch carriers, drop lines, and let numbers lapse, and carriers recycle disconnected numbers to new subscribers. The FCC created the Reassigned Numbers Database because so many numbers are permanently disconnected and later reassigned each year, which is how callers end up reaching someone who never consented.
Every bad number costs something: agent time on dialers, wasted SMS spend, lower answer rates that hurt your caller reputation, and, for reassigned numbers, compliance exposure.
The 5-step cleaning process
- Normalize. Convert every number to one format (E.164, like +15125550182). Strip extensions, spaces and punctuation. Drop anything that is not a possible 10-digit North American number, such as area codes or prefixes that start with 0 or 1.
- Deduplicate. After normalizing, the same number written three ways becomes one. Keep the most recent record.
- Validate. Check each number against live carrier data: is it in service? This is the step that removes dead and disconnected numbers. TrueSearch for Business does this for a whole CSV in about 30 seconds per 1,000 numbers.
- Classify line type. Mark mobile, landline, VoIP and toll-free. Texting campaigns should keep mobile only; landlines cannot receive SMS. Dialer campaigns may treat each type differently for consent and calling rules.
- Run compliance checks for your use case. Suppress your internal do-not-call list, scrub against the National Do Not Call Registry if you make telemarketing calls, and consider the FCC Reassigned Numbers Database for numbers you have consent for. See DNC scrubbing basics. TrueSearch does not perform DNC or reassigned-number checks; use the official sources.
Clean your list in 30 seconds
Upload a CSV. Get back every number marked valid or dead, mobile, landline or VoIP, with carrier.
Start 7-day free trial →How often to clean
- Before every new campaign on an older list.
- At least every 31 days for DNC if you make telemarketing calls: the Telemarketing Sales Rule requires sellers to sync with the Registry at least that often (FTC).
- At the point of capture, by validating numbers in your web forms, so bad data never enters the CRM.
Want to see what a dirty list is costing you? Try the free list health calculator.
Common mistakes
- Validating once at import and never again. Lists decay every month.
- Treating "valid format" as "in service". A correctly formatted number can still be disconnected.
- Texting landlines. It wastes spend and can hurt your sender reputation.
- Assuming a bought list is clean or compliant. Consent does not transfer with a purchased list.