You can’t simply “reuse” an old gamertag if it’s taken, but you can attempt to reclaim it if it’s available or attached to an inactive account.
Steps to Reclaim a Gamertag
Check Availability: Sign in to account.xbox.com or the Xbox app. Attempt to change your current gamertag to the desired one. If free, claim it immediately (first change free; subsequent changes cost $9.99 USD).
“Manage Gamertag” on Console: On Xbox, go to Profile & system > Settings > Account > Choose new gamertag. Real‑time availability check.
Contact Xbox Support: If the tag appears taken but the account seems inactive (0 Gamerscore, last online years ago), contact Xbox Support. They may force a release if the account violates inactivity policies—requires proof of ownership (original email, receipts).
Important Considerations
No Guarantees: Reclaiming is subject to Microsoft’s policies and the tag’s current status.
Fees Apply: First change free; subsequent ~$9.99 (varies by region).
Verification: If the tag is on an inactive account you own, verify via original email/phone.
For the most accurate assistance, always contact Xbox Support directly.