There are two options for purchasing offsets using Green Shipping - manually and automatically. The selection of the mode that you prefer is done in the Shipment Settings section of your account. The image below shows the field that you'll need to change.

If you configure your account to use manual offset mode, then you will need to manually purchase offsets for each shipment. To purchase these shipments, simply log into your account, go to My Shipments, and then click the Buy button next to the shipment you wish to offset. The price of the offset is displayed in the table. When the shipment has been offset, the Buy button turns into the Green Shipping logo, indicating that the offset has been purchased.

If your account is set up for automatic offset purchases, then your shipments will be automatically deducted from your account balance after the shipment is delivered.

No matter what mode of shipment offset you use, full details of your purchase history are given in the Account History section of your account. You will also receive a monthly statement with a summary of your transactions and overall spending for the previous month.