Parents who have to be pursued through the courts or have child maintenance payments deducted from their wages will risk a charge of £300 under a new child support system that comes into force today.
Parents will also face fees if they cannot come to an amicable arrangement on supporting their children financially.
The new system means the Child Support Agency (CSA) will be phased out over the next three years and replaced with the Child Maintenance Service (CMS).
Letters have already been sent to 50,000 parents in England, Scotland and Wales earlier this year warning them of the changes.
More top news
A man is facing jail for killing his toddler son by force-feeding until he "drowned in his food"
The quartet are to work on a 'ground-breaking' project with former Spice Girls manager Simon Fuller.
At least 17 people are dead after an airstrike outside a school in Syria, activists said.