WASHINGTON (Nexstar) — If you still haven’t received your $1,200 stimulus check, you have until Saturday to claim it. The IRS commissioner testified before Congress Friday, urging Americans to register online before Saturday afternoon.

“Tomorrow is the deadline, 3 p.m. eastern time,” said IRS spokesman Raphael Tulino.

Tulino says nearly nine million Americans didn’t claim their checks and may not know they are eligible.

“Generally you are talking about someone who does not normally file a tax return, and a lot of people don’t have to every year, because they don’t meet the minimum threshold of income to file a return,” said Tulino.

Lawmakers grilled IRS Commissioner Charles Rettig about mistakes made while distributing the first round of checks.

“Simple things like getting an EIP for $6.50 instead of $650, and then having to wait nine months for that to be corrected,” Rep. Brendan Boyle (D-PA) said.

The IRS commissioner admits the agency was not properly staffed or prepared to distribute billions of dollars to millions of Americans.

“The Internal Revenue Service employees balanced statutory requirements to deliver these payments ‘as rapidly as possible’ as dictated by the CARES Act, with a need of accuracy and a concern about potential fraud,” Rettig explained.

“As best we could, we began to administer, and that is how we are continuing to administer it as,” Tulino said.

Tulino says the agency is working to correct the flawed checks and is encouraging anyone who thinks they are eligible and hasn’t received a check, to contact the IRS immediately.

“Go to IRS.gov, use a non-filer tool to provide us with that information, and that way we can get you a payment before years end,” Tulino explained.