In particular for charities that perform work the government would otherwise be engaging in, the opposite should be true, and a tax credit to refund 100% of the expenditure should be provided. The reason being is if you donate $100 to a charity that provides for example clothing or meals to welfare recipients, that's $100 the government doesn't need to spend on such programs. However, you are only credited ~$30 towards your tax bill, yet you are net negative $100 that you gave to the charity. The government makes a net positive $70 on your $100 donation to charity. Considering you are spending money so the government doesn't have to, you should be credited the full $100 donation instead of just the $30 that would otherwise go to your tax bill.