Questionable unfurloughing. Do employers have to give written notice taking you off furlough?

[maggiethecat]

A relative of mine says he was not informed that he was taken off furlough in early May and was only asked to volunteer to test safe working practice for return of workers. He declined to volunteer as he was unwell and for several weeks was asked to call in sick/provide a sick certificate. This was confusing as he never received any oral or written confirmation of unfurloughing but he complied.
He also received a letter end of May stating that his furlough was extended to end of July but was later told this was a mistake.
He returned to work end of June at expiry of sick certificate and was not paid for most of June.
Does the employer have to make it very clear, verbally or in writing if an employee is being taken off furlough? If this is not complied with can an employee claim that they were still on furlough and claim pay for that period ( relative was only paid SSP for 'absence" during the period in question).
Can an employee check with HMRC what period an employer has claimed furlough pay on behalf of an employee?

ACAS state that ending furlough should be in writing, but this is not a law, It is just guidance.

I don’t think there would be any way to check the details of an employers claim. Your relative could report them if he thinks there has been a fraudulent claim, but may never know the outcome.

@Florencex - it is probably good practice to end furlough in writing. However I would expect even verbal communication to be clear that someone is being unfurloughed and returned to work which it appears is not the case here. He's not been paid on the basis that he was off furlough and off sick.