The IRS has assured taxpayers of two key concerns during the ongoing federal government shutdown — the tax season start date and the availability of refunds — but accountants say the tax-filing season could still be painful.

Earlier this week, the tax agency said that it would kick off the income tax--filing season on Jan. 28 and taxpayers would receive the refunds they're owed, in spite of the shutdown.

The IRS said it would also recall a "significant portion" of its workforce, bringing them back to work without pay.

But accountants warn that difficult times may still be ahead for taxpayers as the shutdown continues.

"It looks like getting the refund will no longer be the issue, but now it's the lack of support you will get if you try to call — and it will be significant this year," said Tim Steffen, CPA and director of advanced planning at Robert W. Baird & Co.

Here are the hurdles that may stand between you and having your return processed smoothly if the shutdown continues.