Hi Peter
You cannot claim Working Tax Credits:
www.gov.uk/working-tax-credit.
We would normally advise you to seek help from a welfare rights worker where you can give all your details such as date of birth and personal details, but due to the lockdown most advice centres are operating a limited service. You can check by putting your information into one of the online benefit calculators. We do have some excellent guides to help you with your claims in our 'Members Only Guides' section.
gov.uk/benefits-calculators Contact your local Welfare Rights Worker to help with benefit entitlements.
advicelocal.uk Gary