"How much did you spend?"
Completed or changed. Many languages don't have a concept of "tense" but instead a different one of "aspect". But most English speakers don't know the second term unless they've studied linguistics or a foreign language and tend to overuse the term "tense" to cover all kinds of changing verb endings in all languages.
了 can be used with actions in the present or future and actions in the past no not always have to use 了.