A client applied and started his social security benefit in June 2020, which is 40 months prior to his Normal Retirement Age.  This will cause his benefit decrease by 21.67%.  Now he decided to return all the benefits and cancel his application of social security benefits within the12 month cancellable window.  What is the best way to report his SSA-1099 income on his 2020 tax return?  What is the best way to treat the Voluntary Withholding Tax already paid?  

I was planning to report his 2020 tax return as normal, and amend his 2020 tax return after he completed all the repayment.  If this is not the best way, please kindly share.  Thank you so much in advance!