How can i forecast quarterly tax payments in a 12-month cash flow forecast?

[Aurora.M]

I’m trying to build a reliable 12-month cash flow forecast for my small service business, but I keep getting tripped up on how to realistically project my quarterly tax payments. I have a decent handle on my monthly client revenue and operating expenses, but the lumpiness of these big payments makes my cash position look artificially strong for months, then suddenly very tight. I’m not sure if I should just divide last year’s total tax by twelve and smooth it out, or if that’s setting me up for a nasty surprise.

[Andrew81]

I tried smoothing the year end tax by dividing the total by twelve and hoping for a steady monthly hit. It hid the truth for a while but then a big quarterly payment showed up and pulled the rug. Now I plan three buckets revenue regular expenses and a separate reserve that gets funded every month but not smoothed.

[PenelopeWL]

Maybe the real thing is timing rather than size. My forecasts looked solid but cash went out slow while a few clients paid late. I started to track weekly how long it takes to turn work into cash and added a small buffer for the lag. The rest weighed in as expected.

[AdamHG]

Do you have a simple way to model the spike without turning the forecast into a spreadsheet tangle?

[Mason.J]

Sometimes the monthly picture looks right until a quarterly bill lands and I lose a week chasing receipts. I tried setting aside a lump sum at the start of a quarter and forgot it existed, then I found I had to borrow for a week. Not pretty.