Through Blackbaud Merchant Services, there is a security feature that limits high value transactions.  Gifts larger than the transaction limit will be declined.

To authorize transactions for gifts larger than the transaction limit, break the donation up into parts. For example, if processing a transaction in USD that is $60,000, process two $30,000 gifts.

Gifts between the amounts of $10,000 and $50,000 will still be processed, but they will appear as Suspect Transactions.
Default Limits:
United States of America Dollars (USD) - $50,000 or less
Canadian Dollar (CAD) - $52,300 or less
British Pound Sterling (GBP) - $32,700 or less
European Union Euro (EUR) - $38,400 or less

We also offer high limit accounts for organizations that meet certain requirements.  If you would like more information about these requirements, please Contact Support and reference this article.