Upcoming changes to the off-payroll working rules will only apply to payments made for services provided on or after 6 April 2020.
A government report into the off-payroll rules extending to the private sector is due to be published before the end of February.
Ahead of that, HMRC has attempted to give businesses affected by the changes more time to prepare.
Private-sector firms reportedly raised concerns in the review process over what payments for services the rules apply to and from when.
Responding to this, the Revenue said the rules will only apply to payments for services provided from 2020/21.
Previously, the rules would have applied to any payments made on or after 6 April 2020, regardless of when the services were supplied.
The Association of Independent Professionals and the Self-Employed (IPSE) said HMRC's announcement falls woefully short.
Andy Chamberlain, deputy director of policy at the IPSE, said:
"Delaying the start date to when the work is actually performed, rather than paid for, is a sensible move, but it doesn't address the fatal flaws.
"This minor amendment will be little comfort to the many contractors who are already being laid off by companies and panicking about the approaching changes."
The Revenue's clarification indicates the changes to the off-payroll working rules are likely to come into force in April.
Talk to us about the off-payroll rules.