I have some concerns over this particular proposal.
I think, as it's already been published in the media, it could trigger some potentially abusive planning in terms of people just aggregating donations into a single year, giving nothing in other years, or combining spousal donations. I can tell you, as a certainty, that will be the tax advice that will be given. There will be ways to draft around that. There will be anti-avoidance rules to prevent that, but what that will make the rule complicated.
I don't have empirical data for this, but I suggest that the more complicated a tax incentive is, the less likely it is to act as an incentive. If you don't know the baseline above which you have to give, how is it going to incent more donations? I think the bigger the tax incentive, the more the government's likely to take a stronger regulatory posture in relation to charities. That concerns me in terms of preserving the independence of the sector.
I also have concerns regarding the tax equity of treating two donors, who donate the same amount in the same tax year, differently. Two taxpayers give $5,000 under that proposal, and one taxpayer might get a 10% greater incentive, even though they've behaved identically. Tax policy has a rule called tax equity. We typically try to treat taxpayers identically when they behave identically, and this particular proposal departs from that tax policy criterion.
I don't think any of those are fatal to the credit, frankly, but they're at least talking points to be taken seriously.