IRS Commissioner John Koskinen says the agency will slash more than $2.7 billion in 2019 to help the IRS make its 2018 budget proposal.

Koskinen said in a letter to the Senate Finance Committee that the agency is still seeking a funding source for the 2018 budget.

He said he expects a “fair number” of people in Congress and the administration to be able to vote on the budget proposal this week.

He also said the agency wants to find ways to “address and mitigate the consequences of this decision.”

Koskinsen also told the committee that he hopes the IRS can avoid a potentially catastrophic shortfall in 2019 as it seeks to cut costs.

He called on Congress to approve the budget request to ensure that the IRS has sufficient resources to maintain its mission, which is to help taxpayers, and not have “unprecedented and unnecessary” increases in expenses.

The IRS had already been seeking additional funding for 2018 for its $1.8 billion budget, but Koskinens letter said that would have to be approved by Congress, with the revenue-raising measure likely to be used to offset the cuts.

He did not say when that would happen.

Koskins letter also said that the number of employees who will lose their jobs under the plan will be capped at 3,500 in 2019, but said that number will be adjusted for inflation.

The IRS would also be able “to retain” about 3,000 workers who have left for other agencies or private companies, he said.

Koss said the number will not be adjusted based on the number who remain, which will be about 4,000, and that there will be no changes to the IRS’ pay and benefits system.

He also said he hopes Congress will approve the 2018 tax code to ensure the IRS doesn’t lose its job-hunting revenue.

The tax code is being adjusted in a way that would not result in any adverse effects on taxpayers, Koskines letter said.