Best answer by ITGeek123
Two possibilities here:
1) The prices are correct but they're including the 5% VAT not shown online.
2) The tariff that's been loaded onto the smart meters/IHD is wrong.
To work out which, calculate the prices with 5% added and if the prices showing are still out, email OVO so they can update the tariff loaded onto the smart meter: email@example.com
There's a similar topic for wrong prices showing on the Pipet IHD here.
Credit goes to @Darran_OVO