The Inland Revenue Authority of Singapore (Iras) has issued a warning about scams by callers pretending to be its officers.

In an advisory yesterday, Iras said it had received several alerts from members of the public who received suspicious calls.

The scammers would highlight supposed tax mistakes and ask their would-be victims to pay outstanding amounts to a designated bank account, or to provide their credit card numbers to get a tax refund.

In recent instances, the telephone numbers displayed on the scammers' caller IDs included 9781-2000 and 6356-8387.

In some cases, the scammers were able to mask their real numbers and instead imitate Iras' caller ID using spoofing technology.

Iras advised the public to ignore such calls and refrain from transferring any money or providing any personal information to the caller.

Those who have fallen victim to such scams should lodge police reports.

It added that anyone who is in doubt about whether a caller is actually an Iras officer should request for the caller's full name, telephone number and department, and note the time of call.

They should then call Iras' quality service manager hotline on 1800-356-8225 to verify if the call came from Iras.

Iras said that it will not ask anyone to make a payment to a third party's bank account through a telephone call. It also does not offer payment options such as "iTunes credits" or "Steam credits".

It will also not ask for confidential personal details through calls or e-mails.

Confidential documents such as tax return forms, notices of assessment, refund letters or other tax statements will not be sent through e-mails unless specifically requested by the taxpayer.

In a separate press release, Iras said that it has seen an increase in the use of its digital interaction channels, with 58,000 more enquiries this tax season. This is an increase of 66.8 per cent from last year's, and was accompanied by a decline of about 11 per cent in the number of calls and visits.

"Through the convenience of e-services on myTax Portal and digital interaction channels such as the Iras virtual assistant Ask Jamie, taxpayers were able to get instant answers for general tax enquiries," Iras said.

Taxpayers who begin their enquiry with Ask Jamie could also opt to escalate case-specific enquiries to an Iras officer via the Iras Live Chat function. Taxpayers can also choose to opt in for an electronic tax bill by logging into myTax Portal.

Iras also made use of data analytics to deliver greater service customisation to taxpayers.

For instance, by identifying the reasons for repeat contacts from the same taxpayer, it was able to tailor its responses to better address taxpayers' needs.

In addition, Iras also pre-empted the nature of enquiries by identifying recurring key phrases across its digital interaction channels. Iras also noted that more than 97 per cent of those who have filed their tax returns did so electronically, and that 26.7 per cent of taxpayers used their mobile devices to file or view their tax returns on-the-go.