I tried paying my Corporate American Express bill online. The online form told me that the amount due was $2,420.53 (prefilling the box with that exact value), so I selected that balance and authorized payment. When I submitted the form I received the following error:
Error: The amount you attempted to pay exceeds the Total Outstanding Balance of 2420.5299999999997. Please reenter a payment amount that does not exceed this value.
Well, ok then!