Provisional tax: the cost of an underestimated IRP6
Underestimate the second provisional return and SARS can add a 20 percent paragraph 20 penalty plus section 89quat interest. How the thresholds work.
The second provisional return is the one that carries the risk, because the practitioner commits to an estimate of the full year's taxable income before the year's numbers are finally clean, and a figure that lands too low invites a penalty and interest that are difficult to argue away once the assessment is out. Paragraph 20 of the Fourth Schedule to the Income Tax Act governs that penalty, and it bites differently depending on whether the taxpayer sits above or below R1 million in taxable income. C-Suite Holdings runs managed tax operations for South African accounting practices, and the free estimator linked below does this arithmetic for you, before the figure goes in.
How does the provisional tax underestimation penalty work?
SARS levies the paragraph 20 penalty when assessed taxable income turns out higher than the estimate on the second provisional return. The penalty is 20 percent of the shortfall measured in normal tax, not in income, against a benchmark figure, and the benchmark depends on whether the taxpayer's taxable income is at or below R1 million or above it.
The penalty lands on assessment, after the year is filed, which is what makes it easy to miss at the moment the estimate is keyed in. By the time it shows up, the estimate is locked and the working that would defend it is months old, so the place to deal with it is at the point of filing the IRP6.
How far can the estimate fall before the penalty applies?
For taxable income at or below R1 million, the estimate is safe once it reaches the lesser of two figures: 90 percent of actual taxable income, or the basic amount from the last assessment. Reach either one and paragraph 20 does not apply. Above R1 million, only one route remains: the estimate has to reach 80 percent of actual taxable income, and the basic amount stops protecting it.
The same rand of under-estimation is treated very differently at R900,000 and at R1.1 million, so a practice that files both kinds of client needs to know which test applies before it commits a figure.
What is the basic amount, and when does it climb?
The basic amount is the taxable income on the taxpayer's most recent assessment, reduced by any taxable capital gain included in that year. When the most recent assessment is for a year ending more than 18 months before the provisional period, SARS increases the basic amount by 8 percent for each year in between, so an old assessment does not let the estimate sit still while real income grows.
That 8 percent uplift is the detail practitioners most often carry in their heads and least often recompute under deadline pressure, and it is exactly the kind of arithmetic worth pushing to a tool.
Does section 89quat interest apply on top of the penalty?
Yes, and it is separate from the paragraph 20 penalty. Section 89quat interest runs where the normal tax for the year exceeds the provisional and other credits already paid, from the effective date, which for a February year-end falls on 30 September. A voluntary third provisional payment by that date is the lever that keeps the interest down, and it is the one payment with no return attached, just the money.
How do you check a provisional estimate before filing it?
Run the figures through the free SARS provisional tax estimator before the estimate is committed. It works out the IRP6 payment, applies the paragraph 20 thresholds for individuals, companies, and small business corporations, adjusts the due date for South African business days, and shows the indicative section 89quat interest, so the figure that gets filed is one that has already been pressure-tested against both benchmarks.
When does checking estimates become a job to hand off?
The check is quick for one client and quietly expensive across a book, because every company and every individual provisional client shares the same second-period window, and a senior ends up running the same arithmetic dozens of times in the same fortnight. C-Suite Commercial keeps every provisional, VAT, and payroll deadline on one calendar and surfaces the estimates that need a second look, while your reviewer signs off every figure before it reaches SARS.
To see how that would run on your book, book a free Roadmap Session. The free SARS provisional tax estimator is the no-sign-up first step.
Frequently asked questions
Is the penalty 20 percent of the underpaid tax? It is 20 percent of the difference between the normal tax on the benchmark figure and the normal tax on the estimate, so it tracks the shortfall in tax rather than the shortfall in income.
What taxable income avoids the penalty? At or below R1 million, the lesser of 90 percent of actual taxable income or the basic amount. Above R1 million, 80 percent of actual taxable income, with no basic-amount shelter.
Can SARS remit the penalty? SARS can remit a paragraph 20 penalty where it is satisfied the estimate was seriously calculated with due regard to the relevant factors and was not deliberately or negligently understated, so keep the working that supports the figure.
Does the basic amount increase on its own? Yes, by 8 percent a year when the latest assessment is more than 18 months old at the provisional date.
This guide explains how SARS describes the paragraph 20 rule and links the official guidance below. It is general information for South African practitioners, the estimator output is indicative, and a registered tax practitioner remains the person who signs off the return.
Where to go next
- Why the season surfaces these gaps in the first place: provisional tax season exposes operational gaps.
- The boundary that governs all of this: what AI can and cannot do alongside SARS eFiling.
- Run the numbers now: the free SARS provisional tax estimator.