For an expense payment, the books debit Expense and credit Cash. If a 70-dollar payment was entered as 40, Cash was reduced by 30 too little and the expense increased by 30 too little. Correct the difference: debit Expense 30 and credit Cash 30. Keep this book error separate from deposits and checks that are only timing differences.
Worked example
Separate example: bank 300 + deposit 30 - outstanding check 20 = 310. Books 344 - unrecorded fee 4 - payment correction 30 = 310. The verified payment was 70 but entered as 40. The correction is 30, not another 70.
Fictional studio / same closing date
All amounts are fictional dollars. Bank statement: 410; book Cash: 469. Deposit in transit: 60. Outstanding check: 35. Bank interest 2 and fee 6 are missing from the books. A separate cleaning payment of 72 cleared the bank correctly, but the books debited Cleaning Expense and credited Cash for only 42. The receipt confirms 72. No other differences, taxes or adjustments apply.