Several companies now offer to pay car owners a monthly amount in exchange for wrapping their vehicle in branded advertising and driving around as usual. It sounds like easy money for doing nothing extra, but the payment received is still taxable income, and which head of income it falls under depends on whether this is a one-off arrangement or part of a broader commercial activity.
For an individual who simply allows their personal car to be wrapped in advertising in exchange for a monthly payment, without this being part of any broader business activity, the payment is most naturally categorised under Income from Other Sources, since it does not fit neatly under salary, house property, capital gains, or a business/profession the individual is actively carrying on (the car owner is not 'in the business' of advertising; they are simply receiving a payment connected to the use of their personal asset).
Where vehicle advertising income is earned by an entity that operates a fleet of vehicles as a business (a cab aggregator's affiliated fleet, a logistics company with branded vehicles, a bus operator), the advertising income earned on those vehicles would more naturally be aggregated as part of the overall business income of that fleet operation, taxed under business/profession along with the fleet's other revenue streams (fares, freight charges, and so on).
Companies that run vehicle advertising programmes and make periodic payments to vehicle owners may be required to deduct TDS on these payments, depending on the cumulative amount paid to an individual over the year and the applicable threshold for the relevant TDS provision. Vehicle owners receiving such payments should check their Form 26AS/AIS to ensure any TDS deducted is correctly reflected, and report the gross income (before TDS) when filing their return, claiming the TDS as a credit.
For income taxed under Other Sources, deductions are generally limited; ordinary running costs of the vehicle (fuel, maintenance) that the owner would incur anyway for personal use are unlikely to be deductible against this incidental advertising income, since those costs are not incurred specifically to earn the advertising income (the car would be driven regardless of the ad wrap). Where the income is part of a genuine business (the fleet operator scenario), the normal business expense deduction rules would apply to the business as a whole.