How can I count unique clients in a each year

Hello all.

I am trying to obtain the number of clients that shoped in 2018, 2019, 2020, 2021 and so on. I tryed to use Count(Unique) but it gives me the total number of clients that have shoped in our history. When I try to add a formula that restricts the formula to each year, i obtain an error or a wrong number.

Each customer has a customer ID.

So I have two columns in column A is the clients ID and in column B the year he shopped in.

Thank you in advance.