VOA Nigeria
 

My client has obtained a VOA approval letter for myself and colleagues to Nigeria, and I have discussed with the ATL consulate to make sure I'm right, and I do not have to pay online, but rather, must pay at the port of entry, the visa fee. My issue is TIMATIC says one must present not only the approval letter but proof of prior payment when I am not able or supposed to pay the fee online ahead of time. Any ideas if the line from the embassy website saying as much will be enough to handle this at check-in should an agent ask for this "proof?"

You should pay prior to arriving in Nigeria.
see instructions here

Hmm. Yeah I'm seeing "Online Payment may also be made at point of arrival subject to presentation of Visa on Arrival Approval Letter. Master Card, Visa and American Express card are acceptable." Which is consistent with what I was told by the consulate. I have an approval letter already which, from what I understand (since it was arranged by a contact in Nigeria) means the fee is paid on arrival at the VOA desk.

It does say they forward the letter to the airline included in the application, but I mean I have no clue if anyone at the airline is really retaining this stuff lol.

I would pay online in advance for two reasons. One, that way you know you have it, and two, you have no idea how long the line will be if you wait until you arrive.