How can I put Shipping and tax charge on credit card payment where user sets the amount?

It seems this feature is not available where the user sets the amount.

I can do it when I put in a price for the product, but I want to put in a set cost % under tax for any amount the user puts in.

I tried this both with Stripe and away and its the same.

Is there a work around this?

I'm afraid that it is not possible to enable the Shipping and Tax on the stripe payment field when selecting the User Defined Amount as the payment type. The only way to enable this is to add a product.

However, the workaround I could think of to achieve your requirement is to calculate the shipping and tax outside the payment field, then, pass the total amount in the Payment field.

You can achieve this by using Form Calculation Widget to calculate Shipping and Tax. Here's the guide on How to Perform Form Calculation Using a Widget. Then to pass the total amount to the payment field, please refer to this guide: How to Pass a Calculation to a Payment Field.

Cheers.