VAT for purchased materials

Dear All,

We have purchased 10 Diff materials with with 4% VAT Cr & At the end of month my client will decide to avail the 80% VAT for only 4 materials and 20% wants to add into the material cost. It will be decided on the base of consumption of materials

For remaining 6 materials wants to avail credit of 100%. How to achieve this ?

Any idea

regds,

CB