The tax is to be deducted from the actual payment and there is no need of computing notional income in respect of a deposit given to the landlord. If the deposit is adjustable against future rent, the deposit is in the nature of advance rent subject to TDS.
In cases where the tenant makes a non-refundable deposit, tax would have to be deducted at source as such deposit represents the consideration for the use of the land or the building, etc. and therefore partakes the nature of rent as defined in section 194-I. If however the deposit is refundable, no tax would be deductible at source. If the deposit carries interest, the tax to be deducted on the amount of interest will be governed by section 194A.