mediumConceptDesignEntryMidSenior
A customer's app shows one balance and the ATM shows another. How should available balance be defined?
Ledger balance is posted history; available balance is the money the customer can use after holds, uncleared items, earmarks and overdraft limits. Define it once so every banking channel shows the same number.
4 min readUpdated 2026-08-15
Answer
Short answer
Ledger balance is the sum of posted entries. Available balance starts from that ledger balance and adjusts for live card holds, uncleared funds, legal earmarks and overdraft limits. The rule should live in one service and return the components, not just a single unexplained number.
Core banking systems must explain balance differences without forcing operations to inspect raw postings. Core banking controls should make both balances reproducible.
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Likely follow-ups
- A card authorisation is never presented for settlement. What releases the hold, and who decides how long that takes?
- How do you order competing claims on the same funds when a hold, a direct debit and a court order all land on the same day?
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- Your available balance goes negative because a settled amount exceeded its authorisation: whose loss is it, and what does your system do next?
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