Hi @Retired_mod After removing "TABLE" keyword from create or replace statement this function got registered as builtin function. Just to verify that I displayed all the functions and I can see that function--> decrypt_if_valid_user:

Now I am trying to alter the table using below command and it is giving below error:

%sql
ALTER TABLE test.default.sampletbl ALTER COLUMN col_a SET MASK decrypt_if_valid_user

Although I can see this function in the list but still it is not able recognize that function.