As a management consultant earning ₹30 lakh a year, do I have to maintain books of account, and which ITR do I file?

Section 44ADA lets a resident professional with gross receipts up to ₹50 lakh (₹75 lakh if cash receipts are within 5%) declare 50% of receipts as income with no obligation to maintain books under 44AA or to be audited. On ₹30 lakh that is ₹15 lakh of deemed income. Your actual expenses are far below ₹15 lakh, so the presumptive route gives you a larger deduction than your real costs would. Management consultancy is covered because it falls within the notified professions.

You file ITR-4 (Sugam), pay advance tax in a single instalment by 15 March, and keep only enough records to prove the receipts: bank statements, invoices and the Form 16A certificates for the 10% TDS your clients deduct under 194J. If you ever want to declare less than 50% (say a year with heavy expenses), you must then keep books and be audited.

GST: you crossed ₹20 lakh, so registration is mandatory if it is not already done. Consulting is taxable at 18%, invoiced to clients who will mostly claim it as input credit, and the returns are quarterly under QRMP.