What we did, start with accountant and move the function in house as it gives you experience what doc’s you need to keep. As other mention the bi monthly report is due 15 days after the period ends. generally you need keep all invoices (if needed offiical ones) and expenses, many of them are maybe paper copies which you need keep in case they do a check/audit. Our tax office staff is also helpful, the office girl that does it for our company calls them sometimes with questions.
Since you only have one day left, I would ask ChatGPT Agent, Claude Cowork, or OpenClaw to control your desktop/line/phone and do it for you. My Taiwan CPA’s deadline for handing them all the documents was 10 days ago.
And then fill out the 401 form, Fapiao list form, etc…
I’ve done mine for years by hand, but I had my CPA do it for me the first few times for a fee. Since I am consistent, I managed to learn from previous filings.