Thanks for your comment AGB, and sorry I didn’t give enough detail initially. I’ve checked with relevant people internally, and our thoughts are below.
HMRC uses “Gift Aid” (in both the form and their Adjusted Net Income page) to mean that the donation was eligible for Gift Aid in the charity’s hands. We don’t have to claim Gift Aid for the donation to be eligible (and HMRC does not expect donors to confirm this).
If you donated £400 for EAG London and you’re filling out the self-assessment tax return, you would add £400 to boxes 5 and 6 of the Charitable Giving section (as a “one off” donation, because EAG London is not a regular monthly donation). The level of tax relief you receive will depend on your own income levels through the year, and this isn’t something we can comment on.
We aren’t currently planning on claiming Gift Aid on the donations to EAG London to reduce administrative overhead, but we might possibly revisit that in future years. We will take another look at our website language, as we’ve had a few people ask about Gift Aid, and so we may not have been clear enough that our decision on whether or not to claim Gift Aid does not actually impact an individual donor’s tax filing position.
Update here: we’re supporting an EA Summit in Abuja, Nigeria on 6–7 September :)
https://forum.effectivealtruism.org/posts/8eWysFRNK9biZnECY/announcing-the-ea-nigeria-summit