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Determining Whether a Callsign Certificate is Valid

When a Callsign Certificate is issued for a Callsign, any previous Callsign Certificate for that Callsign is rendered invalid. LoTW will reject QSOs digitally signed by an invalid Callsign Certificate.

Each Callsign Certificate has a unique serial number. LoTW maintains a list of your valid Callsign Certificates that includes the serial number for each. To verify that a Callsign Certificate in TQSL is valid, you can compare it's serial number with the serial number displayed by LoTW.

TQSL displays a Callisign Certificate's serial number when you direct it to display that Callsign Certificate's properties:

 

To display LoTW's list of valid Callsign Certificates

1. Log in to your LoTW Account
   
2. Click the Your Account tab
   
3.  In the Logbook Web Account Menu on the left, click the Your Certificates button; LotW will display your Callsign Certificates, with the serial number for each: 
   
 

If the serial number displayed in TQSL matches the serial number displayed by LoTW, the Callsign Certificate in TQSL is valid.