Yes, you can still open a Smart ISA even if you've paid into another ISA this tax year.

There are 4 types of ISAs: cash ISAs, stocks and shares ISAs, lifetime ISAs and innovative finance ISAs. Junior ISAs also exist for children under 18 — but they have their own rules.

Each tax year, you can spread your allowance in any way you like across as many different ISAs as you like, as long as your combined deposits don't exceed your annual ISA allowance of £20,000. The only exception is lifetime ISAs, where there's an annual savings limit of £4,000 and you can only pay into one per tax year.