Keep Meticulous Work Repair Records
When you make a repair to a tenant's apartment, always keep a record of what was done, no matter how minor the work. Keep bills and canceled checks for any materials or parts that were used to do the work. If someone other than an employee made the repairs, keep copies of the bills, as well as any receipts or canceled checks proving that you paid for the repairs. It's also a good idea to have the tenant sign off for the repair work.
All these items could help you out if the tenant later files a decrease-in-service complaint with the DHCR. You will have proof you made the repairs, helping you defeat the tenant's complaint.