The IRS wants quarterly estimated tax payments based on an estimate of what the business will make that year. They want you to pay 100% of the previous year's tax over the course of 4 quarters or 90% of the current year's estimated income.

However, since this is their first year in business and they've only been operational for a few months it's possible to have your "under payment penalty" waived since it's their first year.

Their tax professional should be able to apply the waiver.

Best