It's the time of year many Canadians dread - tax time.

And a computer glitch is making it even more painful for some hoping to get their income tax returns filed early. The Canadian Revenue Agency was forced to shut down its online tax filing system after the bug was discovered.

Some individuals and companies that prepare taxes complained over the last few days that they weren't able to file the returns successfully using the online services, which include Efile, Netfile, and My Account.

CRA commissioner Michel Dorais didn't offer any speculation on what might have caused the problem, but suggested there was no indication that hackers or computer viruses were involved. He added that to protect people's personal information, the system had to be turned off.

"There is no indication that this situation was caused by intrusion, hacking, or computer virus," said Dorais.

"The security of taxpayer information remains paramount as we strive to understand and correct this situation."

Technicians have been working ever since to figure out the source of the glitch, but there's no word on when a fix might happen.

CRA spokesperson Emilia Kotris said brief system disruptions happen, but this incident is "the first time I'm aware of anything lasting longer than an hour or so."

The backlog is already growing. Though tax return preparation company H&R Block is still offering quick refunds to its customers, its employees now have to call CRA offices directly for information.

"We're parking (the returns) on servers . . . and as soon as we get the go-ahead from the CRA, we'll have people just sitting there submitting these returns one after the other," said company spokesperson Cleo Hamel.

Other companies have shut down their services completely until the CRA services come back online.

Tax returns are due by April 30.

For information on other ways to file your taxes, including old-fashioned snail mail, visit the CRA site here.