Are there any documents I will need to complete offline?
This will vary from person to person. If you are resident and bank in the UK it may not be necessary to send any further documentation. However you may be asked to provide further evidence of your identity or bank details.
Any investors choosing a USD$ Portfolio will be required to complete a W8 – the W8 form is provided by the Internal Revenue Service (IRS) to allow non-US persons to receive a reduced rate of taxation on any US-sourced income (including dividends, interest etc.) received from businesses registered or incorporated within the US.
There may also be other paperwork as a result of the FATCA requirements (Foreign Account Tax Compliance ACT).
Can I invest via a Junior Individual savings Account (JISA)
Not at present.