Investing journal: how to keep one you can trust

Memory edits itself. A stock you bought on a hunch becomes, in hindsight, a stock you bought because you saw something others missed. A stock that fell becomes one you “never really believed in”. A journal stops that, as long as you write in it before you know how the call ends.

A journal answers three questions memory can't:

• Was I right, or was I lucky? A call that worked for a reason you didn't write down is luck.
• Do my confident calls do better than the rest? If not, your confidence carries no information.
• Am I better than just buying the index? Only a full record, losers included, can tell you.

Keep it short. A good entry takes five minutes and has six parts:

• The stock and the direction. Bullish or bearish. If you're bearish, say so even if you don't short it.
• The date and the price. The price when you made the call, not the price you later wish you'd paid.
• Your reasoning. Two or three sentences on why the market is wrong about this stock. “It's a great company” is not a reason; the price already says that.
• What would make you wrong. A concrete thing that, if it happened, means the reasoning failed. This is the part people skip and the part that matters most.
• A time frame. Under a month, one to six months, or longer. Without one, a bad call never has to end.
• How sure you are. A simple low, medium or high is enough to check your calibration later.

The investment thesis template has the same structure with examples.

When you sell, or when the time frame runs out, write a closing note: what happened, whether your reasoning played out, and what you'd do differently. The closing note is where you learn. Without it, a journal is only a list of trades your broker already has.

A notebook or a spreadsheet works if you are strict with yourself. The problem is that both can be edited. A row can be deleted, a price fixed, a reason rewritten after the fact, and once that's possible even you can't fully trust the record. We compare the options in spreadsheet vs. app.

SoFo is an investing journal built around that problem. You write the call, SoFo locks the price and the date, and after a 10-minute window to fix typos nothing can be edited or deleted. Your record then shows your process, calibration and returns, so you can see what kind of investor you actually are.