In the past, a hardcopy notice of assessment must be given by the Comptroller of Income tax to the person who is liable to pay the tax. That person is to pay the amount assessed, unless he/she formally objects to the assessment.
On 1 January 2011, in view of the wider availability of technology, Section 42 of the GST Act was amended to implement an “opt-out” approach for the purpose of providing tax notices in digital format.
Instead of requiring taxpayers to provide certain consent before the Comptroller can issue digital tax notices instead of hardcopy notices, taxpayers will now have to opt out if they want to receive tax notices in hardcopy.
With this, taxpayers will have the flexibility to manage their preferences for hardcopy or e-copy at any time.
Source: IRAS, 11 June 2018