How does tax-free allowance on interest on ISA accounts work?

Individual Savings Accounts (ISAs) rules on the website state that "Every tax year you can save up to £20,000 in one account or split the allowance across multiple accounts." https://www.gov.uk/individual-savings-accounts How does this £20000 limit work? Does it mean that if I already opened ISA in the 2023-2024 tax year, and saved £15000 on it, then I can save an additional £20,000 in this tax year (2024-2025)? Then the total would be £35000. Is it true that I still will not need to pay any interest earned on £35000 ISA savings then? Or does £20000 allowance mean that I can have a total of £20000 saved in my ISA? And therefore I can save only additional £5000 in ISA this tax year (because I saved £15000 last year)?

Hi,
You can save 20k (new deposits) each tax year and any interest earned is tax free.
Thank you.

Thank you for your reply! Just to clarify it means that I can deposit additional £20000 to the ISA account this tax year, have total balance of £35000 (including last tax year deposit), and earn interest on all of this amount (35k) tax-free?

Hi Boris

Yes that is correct.

Thanks