Chapter 31
Do I have to close each month?
No — but a shop that never closes a month is a shop that never really knows its cost of goods sold, because that figure only becomes real at the moment of closing.
Closing a month is what turns the stock that left the shelf that month into a cost in the books. Before closing, the shelf and the ledger can genuinely disagree without either being wrong — they are simply waiting for the same event to bring them together.
What closing actually does
It writes one entry: the cost of what was sold that month, taken from the shelf's own figures, credited against the stock account. Nothing about a sale itself changes — revenue was already recorded the moment it happened. Closing is what completes the other half of the story.
A month can be reopened if something was missed, and the entry it wrote comes off cleanly. What it cannot do is let you close a month while an earlier one is still open — the order matters, because each month's figure depends on knowing where the last one left off.
If you skip it
Nothing breaks immediately. The shop keeps selling, and the shelf-based reports stay correct on their own terms. What goes stale is the ledger's own profit figure, which will read as more profitable than the shop really is for as long as the cost of goods sold has never been recognised.