Sales tax collected

Any indirect tax is collected on behalf of Central / State Governments, so it is liability only. The tax not collected but has to pay on account of any ommission on against any assessment is an expenditure.

It is liability 

However if you include this in sales amount, then it is also a exp rahter than liability.

It is liability 

However if you include this in sales amount, then it is also a exp rahter than liability. and it muset be shown in debit side of P&L on payment.