In the future I'll probably want to donate to a UK charity (Humane Slaughter Association). Some people in the UK probably want to donate to a US charity like GiveWell or MIRI. Rather than both donating to foreign charities, we should trade donations so that we can both get tax deductibility / Gift Aid for our donations.
Trading doesn't have to occur only between matched countries. There's a benefit to trading so long as just one side gets tax deductibility / Gift Aid where it didn't exist before. For example, if a UK donor was going to give to a Spanish charity, and if a US donor was going to give to a UK charity, the UK donor should give to the UK charity to get Gift Aid, while the US donor gives to the Spanish charity (without tax deductibility). Trading like what I just described even works for those in the US who have already donated 50% of their income and so can no longer get tax deductions in the current year from further US donations.
We should set up a marketplace for trading donations. According to Tom Ash, trading donations is completely legal.
I created an extremely low-tech platform for donation trading in this Google spreadsheet. Feel free to add your info there, keeping in mind that it's shared publicly on the web.
If something like this gets traction, perhaps we can create a website for the service, not just for EAs but for all donors around the world. I haven't been able to find any existing website for this. I'm not sure if that's because large-scale coordination of donation trading is frowned upon or whether it's just because no one has scooped up this opportunity yet. I'm normally skeptical of startup ideas, but this one seems promising to me.