Goods & Service Tax Reconciliation Tax Difference.

Hello Everyone,

I Have a query regarding Goods & Service Tax, I have a raise a Tax Invoice march - 2021

Basic Amount = 634968.14   GST Amount = 177791.08  28%   Total Invoice = 812759  

But change in purchase tax difference in some items 28% to 18%

Filed IN GSTR-1 & GSTR-3B march

Basic Amount = 634968.14   GST Amount = 173976.84  28%   Total Invoice = 808945 

Tax Difference is = 3814/-

Party used Input Tax Credit against 812759

We paid tax against 808945

What is the way to repay 3814 to party account .