All companies must report under GAAP, and GAAP syas you must report using accrual method of accounting.

FWIW and hopefully not trying to confuse anyone, I believe they do use the cash method for filing their tax returns. Yes, you can use different methods for taxes vs. financial reporting. For investment purposes you should always use accrual based info as that gives you a more accurate gauge of profit/loss. That's why it is required by GAAP.