Just picked this up from a Facebook craft selling group page:
Once registered, you can then send a buyer a direct link to pay the exact amount that they owe you.
e.g. if someone owed me £23.05, I could send them a link www.paypal.Me/myaccountname/23.05 which they simply click on to make a direct payment.
Whether fees are involved, I haven't looked at yet.
This is gradually rolling out to include more countries (currently available to UK, US, Australian and some other European countries). So.....if you are a SELLER from another country (e.g. Ireland), you won't have the facility yet, but BUYERS can use it if they change their country to UK - they can then see the invoice link.
https://www.paypal.me/