Q.The following errors were detected before the preparation of trial balance. Rectify them.

Both are one-sided casting errors found before the trial balance, so each is set right by correcting the single affected account — credit Sales A/c ₹100, and credit (reduce) Purchases A/c ₹400.

These errors are located before the trial balance is prepared, so no Suspense Account exists yet; each one-sided error is rectified by directly adjusting the affected nominal account.

1. Sales book undercast by ₹100 The sales book total was carried to the Sales Account short by ₹100, so Sales A/c was credited less by ₹100. To rectify, credit the Sales Account with ₹100. Rectification: enter on the credit side of Sales A/c — "By Undercasting of sales book ₹100".
2. Purchases book overcast by ₹400 The purchases book total was carried to the Purchases Account in excess by ₹400, so Purchases A/c was debited excess by ₹400. To rectify, credit the Purchases Account with ₹400. …