I have driven into Ghana 4 times now.
The first time was Burkina Faso / Ghana at Navrongo.
Those jovial customs chaps really wanted to see me squirm that day
"No I don't have a Carnet and haven't needed one all the way from London to here, so please find a way to do what every other country in the world is capable of doing, a tempororary permit"
Eventualy they coughed up a permit that is meant only for citizens of ECOWAS. I got 90 days and then found a way to extend it further at their central office in Accra.
The next time I tried to re-enter at Aflao, no problem, spun through same deal.
The last time, again at Aflao the guys said I would have to do a deposit for a temorary import. This actually worked out better, same price but in theory i get my money back when I leave. Again this was supposed to be for Ecowas citizens only. But I tld them the name of a Director of customs at head office and they quickly shuffled the papers in fear of his wrath.
I know Senegal, Mali and Ghana customs inside out, names of important people and all the clunky but endearing systems if anyone wants to know.