A spokesman for the IRS would not speculate on how long the shutdown would have to last in order to result in a delay of refunds.
However, millions of taxpayers tend to be early birds and submit their returns as soon as they can. Households might need the refunds to help pay off remaining holiday debt or just to bolster their savings.
Last year, the IRS kicked off the filing season on Jan. 29.
By the end of that week — Feb. 2 — the taxman received 18.3 million returns and processed 6.1 million refunds, with an average refund of $2,035.
In all, the IRS received 154.4 million returns by Nov. 23 of last year, the most recent date available, and issued an average refund of $2,899.
Providers of tax prep services say they are ready to receive early bird returns.
"Filers can prepare their tax returns now and beginning Jan. 4, TurboTax will securely store completed returns for transmission to the IRS and states once they begin accepting e-file," TurboTax said in a statement.
The company, along with others, also offers refund advances – short-term loans that you can receive within days of the IRS accepting your return. You would then use your tax refund proceeds to pay off the loan.