Starting a sentence with "It" is acceptable in APA but doing so may make sentences needlessly wordy and take the emphasis off of the subject. Pronouns replace nouns, and each pronoun should refer clearly to its antecedent” (APA, 2020, p. 120). In other words, readers should not have to work hard (i.e., search the previous text) to determine to what pronoun the writer is referring.
“It was found that 25% of… (Smith & Taylor, 2016)” is a grammatically acceptable way to begin a sentence.
Although grammatically acceptable, beginning the sentence with "It" instead of naming the subject also leads to the passive voice where the verb (was) precedes the subject/actor (the researchers, Smith and Taylor).
APA recommends avoiding the passive voice in the interest of clarity by using the active voice where the subject/actor of the sentence precedes the verb.
Beginning the sentence by writing
“Smith and Taylor (2016) found that…” or “Researchers found that… (Smith & Taylor, 2016)”
is a more concise and precise (due to the use the active voice) way of presenting the same information.
Although beginning a sentence with it is acceptable, we suggest doing so sparingly and for specific reasons, such as to take the emphasis off of the subject, to avoid overuse of the subject (repetition), or to vary sentence structure (and not start every sentence with an author’s name or with “Researchers…”).
Outside of the specific reasons for using it listed in the previous paragraph, the use of it is often a wasted opportunity to be more concise and accurate in your writing. Avoid ambiguity, be more concise, and use the active voice by replacing the word it with the subject itself.
For more information how to avoid beginning sentences with it (also known as expletive constructions), check out the following resources:
When using it, avoid being vague or ambiguous by referring clearly to a specific noun in the sentence.
Incorrect example: Even though the demographic questionnaire is often used in tandem with the survey, I did not have the participants complete it in this study. (Does the it refer to the demographic questionnaire or the survey?)
Correct example: Knowles (1973) developed the theory of andragogy, and it is often used as a foundational study in research concerning adult learners. (The it in this sentence can only refer the specific noun in the previous clause, the theory.)
Incorrect example: If a participant skips answering a question in the survey, I will code it as incomplete. (What does the it refer to, the question that was not answered or the survey with an unanswered question?)
Correct example: If you download the Abstract Guidelines document, you can refer to it while drafting the abstract for your study. (Because there is only one specific noun, the document, in the first clause, the use of it in the second clause to refer to the worksheet is clear and not ambiguous.)
If a pronoun does not refer clearly to a specific word, rewrite the sentence to omit the pronoun or insert an antecedent.
They and it should be used only to refer to people or things that have been specifically mentioned.
W. W. Norton & Company. (2016). S-6b: Pronoun reference. In The Norton field guide to writing handbook. https://www.wwnorton.com/college/english/write/fieldguide/index.asp