Taxpayers and tax agents trying to lodge tax returns could be left waiting for weeks as technical problems continue to plague the Australian Taxation Office’s IT systems.

Individual taxpayers have been unable to lodge returns via the MyTax lodgement portal since the beginning of the financial year.

Instead they are greeted with 404s, “unexpected system error” messages and timeouts, and have taken to social media in droves to vent about the constant technical issues.

Trying to do my tax return, been getting the same error for 2 days straight. #mytax #mygovau #ato_gov_au

— Luke Gardiner (@luke_gardiner79) July 7, 2015

should i be trying to do my tax online @ato_gov_au? or give up for another day?

— gkachel (@gkachel) July 7, 2015

In addition, registered tax agents are now also reporting problems using ATO platforms, with those attempting to use Windows 7 and Windows 8 hit hardest.

The ATO said it had identified “connectivity issues” with the Electronic Lodgment Service (ELS) used by agents.

“Windows 7 or 8 users may experience connection issues with ELS if you have installed the latest Microsoft patches,” the ATO said in an advisory.

“Microsoft are working on a resolution as a matter of priority and have advised they expect to have a solution within the next couple of weeks.”

Tax agents affected by ELS issues are presented with an error message along the lines of "failed to initialise connection to subsystem”, and asked to call the ATO for an unspecified “workaround”.

That error message is the same one seen by Windows customers earlier this year when a Microsoft patch broke Cisco’s AnyConnect Secure Mobility Client, preventing customers from using it to access VPNs.

Information Age is seeking comment from the ATO on whether the ELS issues relate to the same Microsoft patch.

A spokesman for tax agent H&R Block confirmed that it was also feeling the effects of the ATO systems slowdown.

“Most of the publicity has been around the slow performance of MyTax and e-Tax, which doesn’t directly impact H&R Block since those services are targeted at self-lodgers,” a H&R Block spokesperson said.

“However, the wider ATO system has also been affected and this has also caused the Tax Agent Portal to run slow. This is the interface that tax agents use to manage their client’s affairs with the ATO and is a vital tool in our business.

“Clearly, having this operating at a sub-optimal rate impacts our ability to efficiently service our clients.”

IT mistakes

The ATO initially attributed the problems to an unexpectedly large number of returns being filed, however did not explain why capacity planning and readiness testing in the lead-up to tax time did not surface any errors.

H&R Block’s spokesperson said this was not a good enough explanation.

"All of these systems should be rigorously tested before 1 July to ensure that they can cope with that demand,” the spokesperson said.

“In addition, the level of demand should be anticipated and the systems should be able to cope (it’s not like this tax season is any different to previous ones. This is an annual event).

“The most frustrating thing is that this appears to happen every year about this time. Learning the lessons from previous years should eliminate the risk of this happening.”

One possible explanation is that the network link provisioned for the lodgement services were too small.

Citing an internal ATO source, The Age reported that one of the links could not handle more than 2500 concurrent users, but this could not be immediately verified.

The ATO said on July 7 that it was "working 24 hours a day to fix" the system issues. It reported some progress on July 8, stating that "90 percent of taxpayers trying to lodge are successfully accessing online services and lodging their returns."

On July 9, it said systems for individuals lodging returns were "significantly improved", and a day later noted things were stabilising, although further bugs were due to be ironed out over the weekend.