Open a separate business bank account and start tracking every dollar from day one. The most common regret small business owners have is waiting six months to a year before keeping real books, which means a year of guessing at tax time instead of knowing.
You don't need to become a bookkeeper to get this right. You need a few things set up correctly at the start so nothing has to be untangled later.
Open a dedicated business bank account, even if you're a one-person operation. Mixing personal and business spending is the number one thing that turns tax season into a nightmare, and separating it from day one means you never have to reconstruct it later. Decide on your entity structure with real numbers, too, not a guess. LLC, S-Corp, sole proprietor all have different tax consequences depending on what you expect to make, and it's worth thirty minutes with someone who can run your actual numbers instead of taking a generic answer from a forum.
Pick a bookkeeping system now, even a simple one. It doesn't need to be complicated. It needs to be something you, or someone else, actually updates every month instead of a spreadsheet you'll “catch up on” later.
None of this needs to be perfect on day one. It just needs to exist, so you're never staring at twelve months of bank statements trying to remember what a charge was for.
Add your revenue and website for a full diligence brief, reviewed by a CPA who ran EY's West Coast R&D Tax Credit practice for 13 years.