Forecasting without an MBA
A rough forecast that's reviewed monthly beats a perfect one nobody opens.
Start with last year, line by line
Pull last year's revenue and overhead by month. Project this year's as last year plus or minus an honest assumption. That's your starting forecast.
Three scenarios
Base, downside, upside. The downside is the one that matters, does the business survive it, and at what point do you change behavior?
Update it on the same day every month
The discipline matters more than the spreadsheet. Pick a day, put it on the calendar, and treat it like a customer appointment.
Take your version of this question further
This is one operator-tested angle on the question. Your shop, your size, your trade, and your team change the answer. Ask your specific version inside Ask a Shop Owner to get a response grounded in how owners like you actually handled it.