As a Tax Resident, you are legally required to submit tax returns to SARS every year and declare your worldwide earnings (local and foreign) and then claim any exemptions or tax credits on the foreign earnings.
Importantly, if you do not formally note yourself as tax non-resident with SARS, then you will be seen as a tax resident in SA. Even if you have broken our tax residency tests, being the ordinarily residence test and physical presence test, or there is a Double Taxation Treaty in place, these factors are not going to automatically change your status to tax non-resident. The only way to change your tax status is to formally undergo the relevant legal processes through SARS.
SARS has recently introduced a “SARS Non-Resident Tax Status Confirmation Letter” (example below). This letter was not previously a requirement of the emigration process.