In certain circumstances, public authorities can charge a fee for FOI requests (although this happens rarely).
If the public authority contacts you to tell you that you have to pay a fee, the 20 working day clock will be 'paused'. Once you pay the fee, the clock will start again.
For example, if the authority sends you a fees notice after 10 working days, and you decide to pay the fee, the authority has another 10 working days from the day it receives your payment to respond.
If a fee is charged, you don't have to pay, but you won't receive the information if you don't.
If you're unhappy with the fee that the authority is asking for, you can ask the authority to review this.