Step 1: Understanding the Concept:
A voucher is the source document on which a transaction is entered in accounting software such as Tally.
Most vouchers post entries and change ledger balances.
A few voucher types only keep a note and post nothing.
Step 2: Working Out the Answer:
A memo voucher is a non-accounting voucher.
It records a transaction for reference only, for example an order that may be fulfilled later.
Its amount is not posted to any ledger, so the books and the final accounts of the user stay unchanged.
So the voucher that does not affect the accounts is the Memo Voucher, option (C).
Step 3: Why the Other Options Are Wrong:
Option (A): A post-dated voucher is entered now with a future date. It is posted when that date arrives, so it does affect the accounts.
Option (B): A user-defined voucher is a voucher type the user creates to suit the business. It still posts entries to ledgers.
Option (D): A contra voucher records cash deposits, withdrawals and transfers between cash and bank. It changes both balances.
Final Answer:
The Memo Voucher is the one that leaves the accounts untouched. This is option (C).