Allah destroys interest and gives increase for charities. And Allah does not like every sinning disbeliever.
Quran, chapter 2, verse 276
You earn interest funds when you deposit funds into an interest-bearing bank account such as a savings account.
As a general rule, no Muslim by his/her free choice should invest or deposit his money in an interest-bearing scheme or account.
However, in western countries, when someone unintentionally receives interest funds, they must not use this amount for their personal benefit. In this case it is incumbent upon them to give this amount as sadaqah to the poor who are eligible for zakat. This is not the normal sadaqah which a Muslim gives out of his lawful income with an intent to get reward in the Hereafter. Instead, this sadaqah is meant only for disposing off an unclean and unlawful money, and to relieve oneself from the burden of an ill-gotten gain.
It should be remembered that this amount is unclean only for the person who has received it as interest. The poor person who gets it from them as sadaqah can use this amount for their personal benefits.
If you are a UK Taxpayer, please do not forget to select Gift Aid on your donations which will help with our admin costs. This also ensures all funds raised go towards this wonderful cause.