You get a free £5 when you sign up and make a purchase within 30 days. It's really easy to do and you can refer up to 100 people.
Here is what you need to do:
Click here to join: join.monzo.com/c/v155frf
Enter your phone number on the webpage.
Download the Monzo app and verify your ID.
Top up your account. I just topped up £1 when I did it.
Make a payment of any amount and you will then receive the £5 bonus in your account. Do this within 30 days to receive bonus.