Cash Flow Forecast vs Tax Projection: Two Plans, Two Jobs
Sam's List Editorial | 2026-10-12
Owners with variable income often treat the cash flow forecast vs tax projection question as one question, and it is two. A cash flow forecast tells you whether you will have the money. A tax projection tells you what you will owe. A business can pass one and fail the other in the same quarter.
The two plans are done by different people for different reasons, so here is one firm on each side. System Six is a Seattle bookkeeping and fractional CFO firm, and it is the finance-side firm in this piece, the one to ask about a forecast. Doug Johnson CPA is a Los Angeles boutique CPA firm, and it is the tax-side firm, the one to ask about a projection. This is a contrast, not a ranking, and the order follows the title. Every firm named is a vetted Sam's List member.
What Each Plan Answers: Will I Have Cash, or What Will I Owe
A cash flow forecast projects the cash coming into and going out of your accounts over a period, so you can see your balance on future dates and spot a shortfall before it happens. A tax projection estimates your tax for the year from your expected income, deductions, credits and withholding, so you can plan payments and decisions while there is still time to act. One is about cash on hand. The other is about a liability.
Here is the quick comparison.
Cash flow forecast | Tax projection | |
|---|---|---|
Question it answers | Will I have the cash to cover what is due? | What will I owe for the year? |
What it measures | Cash in and cash out | Taxable income and tax |
Typical horizon | Weeks to months, such as 13 weeks | The tax year, updated as it goes |
Main inputs | Bank balance, invoices, payroll, bills, debt payments | Income, deductions, credits, withholding, estimated payments |
Who usually builds it | A bookkeeper or finance lead | A CPA or tax preparer |
The limitation: both plans are estimates built on assumptions about the future. If a big customer pays late or a deal slips a quarter, both change, so neither is a promise.
Cash Flow Forecast vs Tax Projection: Different Horizons, Different Inputs
A 13-week cash flow forecast, the common form, covers one quarter in weekly columns. You start from the bank balance, add the receipts you expect each week, subtract the payments you expect each week, and carry the result forward. Thirteen weeks is long enough to see a problem coming and short enough that the inputs are still knowable, because you can name which invoices should be paid and which bills are due. It is rolled forward weekly, so the forecast stays 13 weeks long.
A tax projection looks at the whole year. It starts from income so far, estimates the rest of the year, applies the deductions and credits you expect, and compares the result with tax you have already paid through withholding or estimated payments. Its output is a number to plan around, and it gets updated when something material changes, such as a sale, a bonus, equity income or a new hire.
The inputs overlap but are not the same. A forecast cares about when money moves. A projection cares about when income is earned and when a deduction is allowed. Giving both plans the same spreadsheet will blur the difference.
The limitation: a 13-week forecast says little about the year, and a tax projection says little about next Tuesday. Using one to answer the other's question is how owners get surprised.
Where Cash Flow Forecast vs Tax Projection Numbers Disagree: Tax Is Owed on Income, Not Cash
This is the part owners miss. Tax is owed on income, as the tax rules measure it, and not on the cash you happen to have. Several ordinary things push the two apart.
Profit that is not cash. Sales you have made but not collected can be income now and cash later, depending on your accounting method.
Cash that is not an expense. Repaying the principal on a loan is cash out but is generally not a deduction. Buying equipment can pull cash out in one week while the deduction follows depreciation or expensing rules, which for some assets allow much of the cost to be deducted in the first year.
Income that never hit your account. For a pass-through business, profit is generally taxed to the owners whether or not they take it out.
Cash that is not income. Money from a loan, or sales tax you collect and owe to the state, arrives in the account but is not your income.
An invented example. A founder's business shows a profit on paper for the year, but a customer owes a large unpaid invoice and the founder bought inventory for the next quarter. The tax projection shows a tax bill. The cash forecast shows a thin balance. Both are right, and the founder needs to see both before the estimated payment is due.
The limitation: which of these differences applies to you depends on your entity type and accounting method, and the rules have exceptions. Do not assume your cash balance tells you your taxable income, or the reverse.
Using One Plan to Feed the Other
The two plans work best when they pass information. The tax projection tells the forecast how much tax to expect and roughly when to pay it, and the forecast tells the tax plan whether there is cash to pay it with.
Start with the dates. If you pay estimated tax, the payments fall on set dates through the year, and they are not evenly spaced by month, so put the actual dates for your year on the forecast calendar as outflows. Confirm the dates and amounts with your CPA. Payroll tax deposits, sales tax and any extension payments belong on the forecast as well.
Then go the other way. If the forecast shows a cash squeeze in the week a tax payment is due, that is the time to talk to your CPA, before the date, about whether to adjust the payment amount or rules that may limit penalties, such as safe harbor rules, for your situation. Likewise, a deduction that would cut tax but needs cash you will not have is a decision the forecast should test first.
A simple rhythm helps. Update the projection when income changes materially, update the forecast weekly, and compare the two each time an estimated payment comes due.
The limitation: tying the plans together takes someone who understands both the books and the return, and an owner who does not have that person on staff has to bring the two together. A mismatch between the books and the return makes both plans less reliable.
Two Firms, Two Jobs: A Forecast and a Tax Projection
Neither firm below is the answer to both jobs, and the situations differ, so use the profile as a starting point and ask what is in scope.
The forecast side. System Six is a bookkeeping and fractional CFO firm based in Seattle, founded in 2009, with about 41 employees, serving clients nationwide. Its live profile says it serves small businesses generating between $1 million and $10 million of revenue, that the firm was acquired by a searcher in 2021, and that it helps organizations modernizing a finance function after an acquisition. It lists monthly fixed fees starting at $800 a month and a $1 million revenue minimum. The profile does not mention cash flow forecasting, so ask whether a 13-week forecast is in scope and how often it would be updated.
System Six is early in building a review history on Sam's List, so we do not cite a count and describe the firm by what its profile says instead.
The limitation: a $1 million revenue minimum leaves out smaller businesses, and its profile describes bookkeeping and fractional CFO work and does not mention tax preparation, so ask before assuming it covers a return.
The tax projection side. Doug Johnson CPA is a boutique CPA firm in Los Angeles, founded in 2024, with three employees, serving clients nationwide. Its profile positions the firm for growing businesses with $250,000 to $10 million in revenue and for high earners with equity compensation, and it lists minimums of $250,000 of income and $250,000 of revenue. The profile does not mention tax projections by name, so ask whether a mid-year projection, and an update when your income shifts, is part of the work.
Doug Johnson CPA has 15 verified client reviews on Sam's List as of 2026-10-02. Each review is submitted by an individual who identifies as a client of the firm and rates it on communication, subject-matter knowledge, and overall satisfaction. Reviews reflect those individual experiences and do not represent an endorsement by Sam's List. Ratings and rankings are not indicative of future performance or results.
If you have both a bookkeeper and a CPA, ask them to talk. Browse CPAs on Sam's List and ask each how it builds a projection.
Frequently Asked Questions
What is the difference between a cash flow forecast and a tax projection?
A cash flow forecast projects the cash coming in and going out over a period, such as 13 weeks, so you can see future balances. A tax projection estimates your tax for the year from income, deductions and withholding. One answers whether you will have the cash, the other what you will owe.
Why does my cash balance not match my tax bill?
Tax is owed on income, not on cash. You can owe tax on profit that is still in receivables or tied up in inventory, and you can hold cash that is not income, such as loan proceeds. The details depend on your entity and accounting method, so ask your CPA to walk through yours.
What is a 13-week cash flow forecast?
It is a weekly projection of cash receipts and payments for the next 13 weeks, starting from your bank balance. You roll it forward each week so it always looks one quarter ahead. It is meant to catch cash shortfalls early, not to estimate tax.
Should estimated tax payments go in my cash flow forecast?
Yes. Estimated tax is a cash outflow on specific dates, so it belongs on the forecast calendar, along with payroll tax and sales tax. Confirm the dates and the amounts with your CPA, since they depend on your entity and your projection for the year.
Pull your last tax return, your current bank balance and your calendar of due dates, and put them next to each other. The gap between them is the work.
About the author: Kimberly Green is cofounder of Sam’s List, a directory and matching platform for financial professionals.
Were you featured in this piece, or know someone who should be? Share it.