A known tech glitch is affecting some Revenue Services users but the department says personal details have to be sent securely.
Revenue Services has a drive to encourage people to fill out their tax returns online, and it is understood that the majority of residents have adopted this method.
This means that when their tax coding notices are sent out at the end of each year, they are emailed.
A number of people have experienced problems opening their coding notices on their phone or other devices, and the new director of Revenue Service Operations, Jean Mehers, says it is a known problem:
"We’re only too aware of the challenges that some people face when using the Microsoft One Time Passcode process, which is a known Microsoft issue.
“The best way to do this would be to have an online portal that customers can log into and view documents securely, as is the case for online banking and viewing utility bills.
"Secure messaging like this will be included in a future government portal, however, until this is in place, we need to use alternative solutions like the Microsoft-specific tool for encryption, which is what we currently use."
Jean Mehers says for the people experiencing problems there is advice online.
The overall IT project at Revenue Services and the MyGov initiative have been criticised by the new States of Guernsey CEO Boley Smillie as being ineffective, and a questionable use of taxpayers money.
An internal investigation is underway to work out what happened and who is responsible.

Guernsey cyclist becomes MBE in King's Birthday Honours
Guernsey students heading to university to receive Meningitis B vaccine
Guernsey teen set for month-long marathon swim
Guernsey Post introduces new services from early July
Guernsey Waste improves the quality of its free garden compost
Guernsey cat lover to ride the length of Britain in nine days
Unclaimed CI Co-op cash funds community projects
Work to commence on 70 affordable flats and homes in Guernsey