[WARNING: Be aware when dealing in shares with IG]

I sold some US equity shares with a T+2 settlement date on 7th June and as of today (17th June) the funds are still being held as "unsettled credit".

The first response I got from IG support was 

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Unfortunately, we are facing settlement issues with US stocks traded on 07/06. Our Share Dealing Team is currently working with our Custodian to fix this as soon as possible.

We sincerely apologise for the inconvenience. Once this issue is solved, you funds will become available to withdraw.

After lots of waiting and more attempts to get further information I was informed that they were performing an "IT test" which somehow made all trades from that day fail to settle. I was eventually provided with these details:

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    - The tests were performed by our IT Team and Citi to switch us to a new settlement flow, during the test some issues were spotted and the tests were stopped. We were not informed about the time those tests were done.

    - Unfortunately, we haven't been provided yet with any ETA for the funds to settle, the issue is now being discussed between Citi Custodian and Citi Counterparty (CGML). They need to agree the way how to fix this issue quickly. Once again we will let you know as soon as we have any other updates.

So be aware, that at any time IG may decide to perform unannounced tests that affect real live trades and when your funds are gobbled up by these tests they will then hold them for an indeterminate amount of time. An extraordinarily amateurish and embarrassing situation.