Schools have been reassured they won't be left out of pocket if they are set to make a loss from entering students in autumn exams.
If schools' autumn exam fees exceed any rebates they receive for the summer series, the government will pay the difference, according to updated guidance from the Department for Education (DfE).
This applies to all types of schools running additional exams, including those in the independent sector.
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The DfE says it is for individual exam boards to decide to what extent they will offer rebates for the summer exam series, which was cancelled due to the Covid-19 pandemic.
And schools are expected to pay for all students who wish to enter the autumn exams.
However, schools "should not face additional costs for fees, over and above what they would have paid had summer exams gone ahead", the department says.
The guidance states: "We anticipate that the rebates schools and colleges receive will cover the costs of the autumn exams in many cases and we expect them to use these rebates to cover autumn fees.
"If a school or college's additional fees for the autumn series exceed any summer rebate they receive, DfE will provide funding to cover this deficit.
"In order to ensure that no student is disadvantaged by needing to sit autumn exams, these arrangements will cover all schools and colleges, not just those in the state-funded sector."
However the DfE says it will not cover any admin fees "over and above the fees charged by the awarding organisations".
It also says it won't cover costs for English language and maths GCSEs taken by students who did not achieve a grade 4 or higher in those subjects.
This is because the DfE expects schools will already have budgeted for these exams, as they usually take place in the autumn.
Schools will also get access to fully-funded exam venues, if holding the tests on their own sites would cause "disruption to study".
The sites will be accessed through the DfE's "specialist venue supplier", which will be available for bookings from the beginning of the autumn term.
"Alternatively, schools and colleges can book their own sites and submit claims to DfE along with supporting evidence," the guidance adds.
Schools will also be able to claim back invigilator costs if their autumn fees exceed savings they made in the summer.
Geoff Barton, general secretary of the Association of School and College Leaders, said: "We are very pleased that the Department for Education has listened to the concerns we raised about the costs of running an autumn exam series and has responded with this support package.
"It is likely to be extremely logistically challenging to run these exams in addition to accommodating all of next year’s cohort, providing them with catch-up support, and managing complex safety protocols.
"We hope the support package for the autumn series will make this situation a little more manageable."