'I haven’t' or 'I don’t have'

‘Have’ is a very interesting verb because it has many purposes. Sometimes it's an auxiliary verb, for example in the present perfect – ‘I've seen that film’ – ‘have’ here doesn't really have a meaning, it just helps support the main verb ‘see’. Other auxiliary verbs are verbs such as ‘do’ so – ‘Do you have a pen?’ where ‘do’ is the auxiliary verb. But in the example – ‘do you have a pen?’, ‘have’ actually is a main verb, it has some meaning. It means own or possess. So sometimes ‘have’ is an auxiliary verb and sometimes it's a main verb.

In the question we're asked about the difference between ‘I haven't’ and ‘I don't have’. When we use ‘I don't have’, for example – ‘I don't have a pen’ – we're using ‘have’ as a main verb meaning to own or possess: ‘I don't have a car’ – ‘Do you have a pencil?’ We need the auxiliary verb ‘do’ to help support the main verb ‘have’. Occasionally you'll hear someone say – ‘I haven't a clue’, but using ‘haven't’ in this way isn't really usual. So for example we wouldn't normally say ‘I haven't a pen’ or ‘I haven't a book’. We would normally say – ‘I don't have a book’, or ‘I don't have pen’.

In British English, of course, you might also hear ‘I've got’: ‘I've got a book’, ‘I've got a pen’, ‘I've got a new car’. Here ‘have’ is playing the part of the auxiliary verb and this is where we can use ‘haven't’: ‘I haven't got a book’, ‘I haven't got a pen’, ‘Have you got a new car?’

It's important to remember then that ‘have’ can be a main verb or an auxiliary verb. If it's a main verb you need another auxiliary to support it, such as ‘do’. ‘Do you have a new car?’

When it's an auxiliary verb it's helping another verb – ‘Have you got a new car?’ But please try to avoid – ‘I haven't a new car.’