The IRS has proposed an update to the Form W-4 that it says will increase its accuracy and reduce its complexity. But experts say it may prove a bit more difficult for employees to complete.

The form, which is used to help employers know how much to withhold from paychecks for federal taxes, requires more detail about outside income, deductions and exemptions on the form itself. Those used to be exiled to worksheets that not all employees completed.

The IRS is making the update in the wake of the overhaul of federal tax law. It’s a draft and open to public input until July. A final version will take effect in 2020. Existing employees will not have to fill out the new form, but new hires will come Jan. 1.