"How many days has it been since I purchased the subscription" or "How many days have it been since I purchased the subscription".
My limited knowledge says me "has it been" is correct but Google translator translated this into "have it been". Kindly clarify this to me.
A possible answer to your example question is "It has been xx days ...."
From the answer, we see that has is the right one.
How many days has it been since I purchased the subscription?
Although the subject is days, which is plural, we need has, to agree with the dummy subject It/it.
Ngram shows that "How many have it been" is not used.
