NumberResearchThousands-blocks in 443-423
This prefix’s ten 1,000-number blocks and who holds each — 10 on record · from the daily NANPA thousands-block report, 09/20/2026
The ten 1,000-number thousand-blocks inside prefix 443-423 and who was initially assigned each. Under pooling these blocks often belong to different carriers — the single prefix-level “assignee” is usually just the pool / code holder, not who holds the numbers. ← all 443 blocks
Most active assignees, all time — NPA 443
New assignments by month
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2005-09-27 | 443-423-0XXX | 0000–0999 | Assigned | PAETEC ITEL, LLC | 829J | BALTIMORE | MD |
| — | 443-423-1XXX | 1000–1999 | Reserved | LEVEL 3 COMMUNICATIONS, LLC - MD | 6119 | BALTIMORE | MD |
| 2004-12-29 | 443-423-2XXX | 2000–2999 | Assigned | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC | 6855 | BALTIMORE | MD |
| 2004-12-29 | 443-423-3XXX | 3000–3999 | Assigned | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC | 6855 | BALTIMORE | MD |
| 2003-08-12 | 443-423-4XXX | 4000–4999 | Assigned | VERIZON MARYLAND, INC. | 9212 | BALTIMORE | MD |
| 2003-08-12 | 443-423-5XXX | 5000–5999 | Assigned | VERIZON MARYLAND, INC. | 9212 | BALTIMORE | MD |
| 2003-08-12 | 443-423-6XXX | 6000–6999 | Assigned | VERIZON MARYLAND, INC. | 9212 | BALTIMORE | MD |
| 2003-08-12 | 443-423-7XXX | 7000–7999 | Assigned | VERIZON MARYLAND, INC. | 9212 | BALTIMORE | MD |
| 2004-05-06 | 443-423-8XXX | 8000–8999 | Assigned | VERIZON MARYLAND, INC. | 9212 | BALTIMORE | MD |
| 2004-12-29 | 443-423-9XXX | 9000–9999 | Assigned | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC | 6855 | BALTIMORE | MD |
Source: NANPA Thousands Block Assignment Report (All Regions, Public), file date 09/20/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.