Sometimes donors attempt to give a large donation and the transaction is declined, and we're asked if this is refused on our end due to a maximum donation amount.
The answer is NO, there is no maximum donation amount. However, it is quite common for a donor's credit card company to decline transactions that are flagged as potentially suspicious. This happens most frequently - by far - with American Express. The most common situation is a donor attempting to give a large donation with an Amex card that is not commonly used.
To alleviate this problem, the donor can simply contact their card provider and let them know the donation is a legitimate transaction, then re-attempt the donation.