Heavy goods vehicles registered outside Britain and Northern Ireland will be charged up to £10 (€12) a day to drive on UK roads for the first time from today.
All lorries weighing more than 12 tonnes will be charged the new levy which is expected to hit Irish hauliers in border counties particularly hard.
The levy, which will be capped at £1,000 a year, is intended to level the playing field for British truck drivers who have to pay tolls and levies when driving in Europe.
Hauliers will have to pay the levy before entering the UK, either online or by telephone.
Failure to pay carries a fixed penalty of £300 or a maximum fine of £5,000 if the matter goes to court.
The levy in Northern Ireland will be enforced by the Driver and Vehicle Agency, initially by manual checks and then by automatic number plate recognition cameras linked to a database.
Two roads in Northern Ireland are exempt from the levy, because they straddle both sides of the Irish border.
They include part of the A3, west of Clones, Co Monaghan and the A37, which is a main through route between Dundalk in Co Louth and Castleblaney in Co Monaghan.