A very difficult query

while calculating income u/s 44AD it is assumed that the disallowances u/s 40, 40A and 43b is already considered. hence there is no need to disallowed vat liability. 

Provisions of section 28 to 43C will not be applicable when return is filed under section 44AD. Hence VAT liability which is not paid will not be disallowed.

I hope this is clear to you

Any deduction allowable under the provisions of sections 30 to 38 shall, for the purposes of sub-section (1), be deemed to have been already given full effect to and no further deduction under those sections shall be allowed : Provided that where the eligible assessee is a firm, the salary and interest paid to its partners shall be deducted from the income computed under sub-section (1) subject to the conditions and limits specified in clause (b) of section 40.

but an eligible assessee who claims that his profits and gains from the eligible business are lower than the profits and gains specified in sub-section (1) shall be required to keep and maintain such books of account and other documents as required under sub-section (2) of section 44AA and get them audited and furnish a report of such audit as required under section 44AB