The SDI allows you to set the following querystring parameters (which must be UrlEncoded).
The ID of the active JustGiving charity. You can obtain that ID by calling our CharitySearch API
A decimal number, optionally including two decimal places.
50 characters of free text for your reference. This is returned on the JustGiving API as "thirdPartyReference".
We currently only support single donations
A Url encoded Uri. If an exitUrl is supplied, after the "Processing" page, the user is redirected to this location. We suggest that you encode some kind of unique identifier into this exitUrl so you can identify the user.
You can set the donation form to default to one of our selected currencies.