The growing popularity of mobiles has been a conundrum for government departments and other large service organisations.

Inland Revenue will now accept calls to all its 0800 lines from mobiles, removing a small frustration for people who rely on smartphones for calling.

One of the drawbacks of relying on mobiles for calls is that it is not possible to call some freephone numbers.

That is because the organisation being called has to pick up the tab for incoming calls, and those made from mobiles cost them more.

For that reason, phone companies give businesses and government agencies that have freephone numbers the option of blocking mobile calls.

Inland Revenue operates several 0800 lines which separately handle queries related to services such as income tax, Kiwisaver and child support.

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Spokesman Peter van Schaardenburg said calls from mobiles had previously been barred to most of its more popular lines.

But a change had been possible as a result of a negotiation with phone companies over rates, he believed.

Work & Income also accepts 0800 calls from mobiles, and cautioned last year that the costs of doing so were rising, as people used their smartphones for more and more calls.

The Social Development Ministry struck a deal with Spark, Vodafone and 2degrees last year over mobile data, in a bid to encourage more beneficiaries and superannuitants to instead access its services online.

The three telcos agreed to "zero-rate" mobile data traffic to its websites.

That means Work & Income clients and pensioners don't now have to pay normal casual mobile data charges or eat into their mobile data allowances if they use their smartphones to book appointments, check their entitlements or declare wages.

Instead, any charges associated with accessing the sites will be a fraction of a cent.

Inland Revenue customer services manager Patrick Crawford said the inability to call its 0800 lines from smartphones had been "a common frustration" for businesses and individuals who had ditched landlines.

The department received an average of 13,000 calls every weekday and the change was another step in the direction of making the department easier to deal with, he said.

Inland Revenue would also allow "call backs" to mobiles if people didn't want to wait to get through to its contact centre, he said.