NatWest and Royal Bank of Scotland have reduced the buffer from which they start charging customers £6 per month for dipping into an authorised overdraft, from £100 to £10.

From 12 July, the banks, both part of the RBS group, will charge customers £6 per month when they go into authorised overdrafts by more than £10 (see our Best Bank Accounts guide if you're thinking of switching).

If you had a £1,000 overdraft and went £50 into that overdraft, you currently wouldn't incur a charge. But after 12 July, you'd be charged £6.

Customers with the paid-for Select Platinum, Advantage and Royalties Gold and Black accounts will escape these charges, as well as those with graduate and student accounts.

Affected customers will be written to over the next two months.

This one-off charge is on top of the interest charged for being overdrawn. Most NatWest and RBS customers are charged between 14.89% EAR and 19.89% EAR, payable if you exceed a certain threshold, which differs depending on the type of account.

Graduate account fees

There are also changes for customers with unauthorised overdrafts.

From 12 July, graduate account holders will be hit with a £6 monthly fee for dipping into an unarranged overdraft (see our Graduate Bank Accounts guide for the best accounts) – currently there is no fee for doing this.

But the charges for all current account customers who go into unauthorised overdrafts will be capped at £90 per month, down from the current £186. Customers who go overdrawn by more than £6 will still be charged £6 per day.

All NatWest and RBS customers in an unarranged overdraft also incur a £6 daily fee for each bounced item up to a maximum of £60 a month.

An NatWest and RBS spokesperson says: "We have made these changes as a result of a regular review of the facilities we make available to our customers. A new fee has been introduced, however, others have been removed or capped across our range of current accounts."