If your carrier sends customs forms or commercial invoices to your ShipStation account for your international orders, you can then print them through ShipStation to include with the shipment.
ShipStation does electronically submit customs forms for UPS and DHL Express shipments. See the Electronically Submitted Customs Forms section below for more details.
You can access your customs forms in three places:
The Forms column in the Shipments tab
The Shipments section of the Order Details screen
The Print menu in the Active Batch screen
The Forms column in the Shipments grid will contain a form icon 
if a customs form or commercial invoice is available to view and print.
If you do not see the Forms column, go to the Columns drop-down and select Forms. ShipStation will add the Forms column on the right side of the grid. Scroll to view, and drag and drop the column to change its location in the grid.
The Order Details will also show the form icon in the Shipments section.
To view or print, do one of the following:
Click the form icon
and select a print method from the printing pop-up.-
Click the Docs drop-down menu and choose Other Forms. Then choose a print method from the printing pop-up.
If you process your orders in batches, you can also print all forms contained within a batch from the Shipment tab.
Click Batches in the left-hand sidebar.
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Click Active to view your active batches and select the batch you want to print.
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Click the Print menu and choose Other Forms.
The number of customs forms or commercial invoices in the batch will appear in parentheses.
Select your print method from the print pop-up screen.
ShipStation will then print all customs forms or commercial invoices contained within the batch.
ShipStation automatically submits your customs forms electronically for UPS and DHL Express shipments.
Electronic form submission occurs when you create the label for any shipments that:
Require a customs form
Are sent by UPS or DHL Express
Each carrier requires a different electronic submission protocol.
EDI: Electronic Data Interchange, used by UPS
PLT: Paperless Trade, used by DHL Express
The PLT feature is enabled by default for DHL Express users shipping through ShipStation. Certain restrictions may apply based on destination, so be sure to check with your carrier account representative for details.
UPS users must apply to UPS directly before EDI is enabled for a UPS account. Once enabled on the UPS side, it will be enabled on the ShipStation side. To apply online, go to the UPS Paperless Invoice Enrollment page and click on the option to enroll in the paperless invoice.
UPS forms submitted via EDI will have EDI printed on them underneath the tracking barcode on the label.
If you see INV instead of EDI in this location, that means the customs form will not be submitted electronically to UPS.
If this happens, you will need to print the forms through ShipStation and include them with the Shipment. Contact UPS to enable EDI on your UPS account so forms will be submitted via EDI in the future.
DHL Express submits customs forms electronically by default for all accounts when shipping to countries that support Paperless Trade.
DHL Express will print C-PLT on the label if forms were submitted.
Additionally, the archive document that prints with the DHL Express label will print Paperless Trade in the Features / Services section.
If the label does not display PLT and the archive document does not list Paperless Trade below the Features / Services section, you will need to print your customs forms. Check with your DHL Express account manager to find out if the forms need to be attached to the box or handed over to the driver.