Short answer: fill the landlord, tenant, period and rent, then download the receipt. Cash payments above ₹5,000 get the revenue-stamp reminder automatically. Print it and have the landlord sign — an unsigned printout is not proof.
Why employers reject rent receipts
Usually one of three things is missing: the landlord PAN when annual rent crosses ₹1,00,000, the mode of payment, or the landlord signature. A receipt with no PAN and no signature looks like it was made by the employee, and that is exactly what an assessing officer checks during scrutiny.
One receipt per payment, not one per year
Generate a receipt for each month or quarter you actually paid. A single annual receipt covering twelve months is accepted by some employers, but monthly receipts match the bank statement line by line and are much harder to question.