Employers who intend to use the furlough scheme have two days to place workers on leave or risk losing entitlement to the support.
From 1 July 2020, only employees who have been furloughed for at least three weeks on or before 30 June 2020 will be eligible for the scheme.
Any employees not yet furloughed, must be furloughed no later than 10 June 2020 to be eligible for support in the final four months of the scheme.
Chancellor Rishi Sunak recently extended the furlough scheme until 31 October 2020, and more than a third of the UK's workforce are on leave.
Sunak is expected to issue further guidance on the second iteration of the furlough scheme on 12 June 2020.
Jeremy Coker, president at the Association of Taxation Technicians, said:
"Unless an employee has been furloughed at some point between 1 March and 30 June 2020, for a minimum of three continuous weeks, it will not be possible to furlough them between 1 July and 31 October.
"Employers should be aware that from 1 July, the number of employees they can include on claims for periods from that date will be capped.
"The cap will be equal to the maximum number of employees previously claimed for in the first three months of the scheme."
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