The answer to this depends on the type of debt they are collecting, and whether they have visited before. If they are collecting an unpaid CCJ and this is their first visit, they cannot force entry. There are however certain situations where bailiffs can force entry, including:
Collecting unpaid fines: As a last resort they can force entry, whether they have been in your home before or not, if they have a Magistrates Court warrant.
They have gained peaceful entry before: If they have been in your property before by means of ‘peaceable entry’, they can force entry when they next visit if you do not allow them in.
County Court bailiffs entering a commercial property: They can only do this if there is no living accommodation attached. They need permission from the court to force entry into any commercial property.
Collecting income tax or VAT:  They must also have permission from the court – for example a tax collector with a warrant from a Magistrates court. And they can only do this if they failed in a previous attempt at ‘peaceable entry’.
Following goods: Where entry was gained from a different property and made a levy, and they are now following the goods.
If you are worried about a bailiff forcing entry to your property and are expecting a visit, contact PayPlan on 0800 316 1833 for free advice.