Hello hemeltrophy,

You can enter a custom tax from the VAT section and make sure that Purchase tax is reclaimable option is checked.

Here's how:

1. On the left panel, click Taxes and select VAT.
2. Click the Add tax button located in the upper right-hand corner.
3. Select Custom tax and enter the tax information.
4. Put a check mark on the This tax is collected on purchases box.
5. Enter the percentage and put a check mark on the Purchase tax is reclaimable box.
6. Click Save.

Once done, you can create the FedEx invoice as a bill and check the box for VAT Reclaimable.

I'm adding this sample screenshot for your reference:

 If you have any additional questions about VAT, please don't hesitate to ask. Thanks.