Under normal conditions, payments on the Lightning Network achieve a 90% to 99%+ success rate, depending on factors such as liquidity, routing, and network connectivity. Liquidity is the primary factor that influences whether a payment can be successfully completed.

Payments may fail when there is insufficient liquidity in the required channel, and no viable alternative route across the network can be found to process the transaction. While micro- to mid-tier transactions are typically processed with high success rates, larger payments may face more routing constraints and therefore a higher risk of failure.

If a payment fails, the funds are automatically returned to the sender. There is no partial completion. The HTLC mechanism ensures that if the payment cannot be delivered in full, it is not delivered at all.

The Lightning Network was built to enable efficient, high-frequency Bitcoin transactions. As overall network liquidity continues to grow, the size of payments that can be reliably processed is also increasing, already reaching several thousand dollars per transaction in many cases without impacting the network's ability to handle high-volume transactions.