Why the estimate matters
The second payment must be based on a reasonable estimate of the year's taxable income. Estimate too low and SARS can add an underestimation penalty and interest. Your books are the evidence for the estimate.
Other year ends
A company with another year end pays its first IRP6 six months into its year and the second at its year end. The deadline calendar works the dates out from your own year end.
How Bookkeeping & Invoicing helps
Your income and costs are in the books as you go, so the estimate comes from real figures, not a guess. The year-end pack lays out the IRP6 estimate with the return, and the deadline calendar emails you before each payment is due. You or your accountant submit on eFiling.
A note
This is a plain-English summary, not tax advice. Check your own case with SARS or your accountant.