Information about interest rate capping on overdrafts is here:
https://monzo.com/help/budgeting-overdrafts-savings/capped-overdraft-fees-coronavirus
How it works
At the end of the month we’ll calculate what we would have charged you on our fixed fee pricing (including the £20 fee free buffer) that applied before 1 April 2020. If your interest charge is going to be more than the fixed fee, we’ll cap it automatically at the lower amount.
If you have a limit of up to £1,000
We won’t charge you more than 50p per day for the days you’re overdrawn, which means a maximum charge of £15.50 per month.If you have a limit greater than £1,000
We won’t charge you more than 50p for the days you’re overdrawn £1,000 or less, then £1 for days where you’re using £1,001–2,000, and £1.50 for days where you’re using £2,001–3,000. That’s a monthly maximum of £31 and £46.50 respectively if you’re overdrawn for your full limit for the whole month.
Also as speculated previously:
The arranged overdraft interest charges will be capped from 14 April 2020 for three months.
Meaning from 1st April → 14th April, you’ll be charged your personalised interest rate.