Which one is correct ''there has been'' or ''there have been''?

Which one is correct? It depends on how many things or people you would like to mention.
 
If it’s only one (or your word is an uncountable noun), use ’has been’:

• There has been a slight delay. I’m afraid you’ll have to wait a few more minutes before we can start.
• There has been a change of plans.
• There has been a lot of speculation over who the new minister will be.

 
Let’s look at some examples with plural forms:

• Although there have been some improvements, we’re still not satisfied with your service.
• There have been discussions concerning their new product.
• There have been some proposals for a manned mission to Mars.

 
As you can see the words improvements, discussions and proposals are in the PLURAL FORM, so in these sentences ‘there have been’ is used.
 
When using the verb ‘to be’, aways make sure that its form matches the subject and check if it’s singular/uncountable or plural.
 
SINGULAR/ UNCOUNTABLE
 

• There is a cat under my blanket.
• There is some milk on her wiskers.
• There has been a fight.
• There hasn’t been much noise.
• There was a dog here before, but my cat has scared him away.
• There was a lot of tension in the air.

 
PLURAL

• There are some cats under my blanket.
• There are some pieces of cheese in my bed.
• There have been some mice in the house.
• There were a lot of flowers in my garden before, but my cat has eaten them all.