One of the guiding principles at Slatecard.com PAC is our commitment to openness, honesty, and transparency with the Slatecard community. That's why it is important for us to let you know as much about the backend processing of transactions as possible so that you feel comfortable using our utility.
While we fully explain the processing of transactions in our "Frequently Answered Questions," it is important for me to break it down in this space which covers a larger audience based on the past few days' site analytics.
To be clear, no matter what contribution you make to a candidate or as a gift to Slatecard.com PAC, 95.5% of your transaction will arrive in the form of a check from Slatecard.com PAC to that recipient candidate or committee with all of the FEC-required donor data to properly report the contribution. In other words, the fee which is charged to the candidate for using Slatecard.com PAC is 4.5%.
A majority of that fee goes to Authorize.net and the merchant provider who literally makes the transaction. Their fees include monthly fees, per transaction flat fees, and varying percentage fees based on the type of credit card used. We also pay a monthly fee for an SSL certificate to safely and securely encrypt your personal data along with fraud protection service to protect our users as best as possible.
Here's a chart to help explain how this process works based on different donation sizes:

As you can see from the chart above which only accounts for a few of the fees associated with operating a comprehensive online merchant system, even at a rate of 4.5%, the cost of processing lower dollar contributions exceeds the fee. That's why any remainder of the fee for higher-dollar contributions will be used to help offset low-dollar
contributions, pay our monthly fees for the merchant gateway, and help pay other expenses associated with running (and
hopefully expanding) the PAC. Without a processing fee, we could not ensure the longevity and viability of a utility with a national scope.
By way of comparison, the cost of transacting donations using a third-party system like PayPal is about the same as Authorize.net's fee structure (monthly fee for merchant gateway, per transaction fee, percentage of total dollar amount fee). Once we have some relevant statistics, e.g., average donations, type of credit cards being used, and whether people want more options (like PayPal), we will review and amend our structure and/or provider as appropriate.
As always, we want to ensure that you understand as much about the process as possible to better understand the motives of the utility. In other words, the goal of the 4.5% fee is to essentially break even
with our cost of doing business while providing a flat fee rate that
our community and the recipient candidates easily understand at all
times.
Therefore, we are 100% reliant on our community to help us operate and expand beyond the beltway.
That's why on each donation, we ask for a voluntary monetary "tip" to
help us do just that. If we don't offer a good service to the
community, and if you don't think the work we're doing is
valuable, we recognize that people won't support our efforts. But for
those that do support us, we promise to make you proud to have helped.
If you have feedback, please send us an email at team AT slatecard.com. (As we noted on the blog, comments are disabled as we work through a bug.)
UPDATE 11:50 PM: A Slatecard user from Maine has asked if other sites, like ActBlue, charge a transaction fee. The answer is yes. Earlier this year, ActBlue wrote a blog post on how they had to make the organization sustainable and "built to last":
Moving political money properly takes a lot of gear ($) and staff
($$). As ActBlue grows into the premier fundraising platform for
Democrats up and down the ballot, Auburn Quad's responsiblity to
maintain and scale the system grows as well. These things are anything
but cheap.
Here's how it all works. Auburn Quad charges a service fee of 3.95%
against gross contributions. Most of that fee ends up going to the
credit card companies; about 1.5% stays at AQ. That 1 1/2 cents on the
dollar pays for pretty much everything behind the website: computers,
the programmers, and the coffee; or in specific terms, all the
additional transactional costs borne by AQ to receive and remit
contributions on your behalf.
Meanwhile, the real action still lies inside ActBlue. Your tips and
other generous contributions to the PAC allow us to extend our
operations into new states, assist thousands of campaigns with their
online fundraising, hold training events across the country, share best
practices with our partners, and most importantly, offer these tools
and top-flight customer service *for free to everyone*. ActBlue is
working to empower a new class of active Democrats who can reshape the
country's political dynamic and grow our party for generations to
come. Every last bit of this work is funded with your contributions.
Freed from the financial responsibilities of the payment platform,
ActBlue spends every last political dollar on politics.
We're building Slatecard to last and grow quickly -- from day one.