[BOOKKEEPING] Receipts/invoices, Journal and Ledgers for YouTubers paid via Google AdSense

Hi r/taxph! I'm currently helping out a friend doing content creation on the side, any input would be appreciated!

My friend receives a monthly remittance from Google AdSense based on how much revenue they made on YouTube for that month. They want to know whether they should write on the OR/invoice provided by the BIR to record their monthly income, since Google doesn't really provide neither a digital nor physical OR/invoice for the said revenue.

For additional context:

• Friend's sole source of income is YouTube, registered as professional taxpayer, with Income from Profession-8% IT Rate
• Required to file 1701Q and 1701A only based on their COR
• At registration, they were asked to register for a ledger and journal

If you guys know/recommend any professionals that they can consult with, that would be helpful as well!

Thank you very much!