You can make a payment:

 

over the phone (800) 653-7893


or mail a check to: 
 

Liberty Mutual Insurance 
PO BOX 91012

Chicago, IL 60680-1110

Overnight Address:

Liberty Mutual Insurance

Attn: Payment Processing Center BC

100 Liberty Way

Dover, NH 03820

You can pay over the phone using the routing and account number from your check