Non-Availability of C-Form

What is the consequence of non-submission of C-Form when the sale is effected from the  state of Gujarat?  Option 1- If one has pre-hand information that C-Form will not be available Option 2 - if it is known at the time of sales Tax assessment that C-Form would not be available. Will the Tax be charged at a Flat rate of 10% or  the prevailing local VAT rate which is 5% (4%+1%) on that particular item ? If it is known beforehand that C-Form is not going to be made available - whether 5% CST should be charged in the Invoice or 5% (4%+1%) GVAT  be charged ?