
If you claim tax credits and have returned to work after being furloughed but are still temporarily not working your normal hours due to COVID 19 you do not need to tell the HMRC tax credits office. They will continue to use the information they already have and treat claimants as working their normal hours until the Job Retention Scheme closes until 31st October 2020, even for those not furloughed.
Claimants can still report other changes in income, childcare and hours in the normal way. However, you must tell HMRC tax credits office if you or your partner lose your job, or are made redundant, or cease trading.
PAYadvice.UK 7/8/2020