21Relay
Intermediate curriculum
Lesson 1216 minReviewed July 2026

When Bitcoin Transactions Go Wrong

Learn what a wallet may mean by failed, rejected, missing, dropped, replaced or merely unconfirmed—and why those states require different responses.

Learning outcomes

By the end of this lesson, you should be able to

  • Failed creation, node rejection and delayed confirmation are different states.
  • An unconfirmed transaction is not automatically invalid.
  • Each node maintains its own mempool.
  • RBF and CPFP should be used through understood wallet features.
1

Start by identifying the actual state

A wallet can fail before broadcast, a node can reject a transaction, or a valid transaction can remain unconfirmed after broadcast. These are not the same event.

Locate the transaction ID when one exists, check your own wallet or node first, then compare with a reputable explorer if necessary. Do not rebroadcast a newly constructed payment until you know whether the original spends were accepted.

2

No transaction ID usually means no broadcast

A wallet may fail to build or sign because funds are locked, the amount plus fee exceeds available UTXOs, the destination is invalid, the wallet is offline or required signing devices are unavailable.

Correct the displayed cause inside the wallet. Never paste a seed phrase or private key into a support website to repair a payment.

3

A node can reject a signed transaction

A node checks consensus and local relay policy before accepting a transaction into its mempool. Conflicting inputs, non-final locktime, malformed signatures, policy limits or an inadequate fee can cause rejection.

A rejection does not automatically mean bitcoin was lost. The referenced UTXOs remain spendable unless another valid transaction has already spent them.

4

Unconfirmed is not failed

A valid transaction can wait because its fee rate is below current demand or because an unconfirmed parent must confirm with it. Mempools are local, so a transaction can appear on some nodes but not others.

If timing matters, use only fee-bumping features your wallet explicitly supports. Replace-by-fee can replace a qualifying transaction; child-pays-for-parent can make a related package more attractive. Do not improvise raw transactions with valuable funds.

5

Dropped, replaced and conflicting transactions

A node may evict a low-fee transaction when its mempool fills or forget it after restart. Another node may retain it, and the transaction can be rebroadcast later, so disappearance from one explorer is not proof that it can never confirm.

A replacement or confirmed conflict spends at least one of the same inputs. Follow the transaction that the network ultimately confirms and let the wallet reconcile before attempting another payment.

6

A safe troubleshooting order

Check the destination, amount and wallet status; find the transaction ID; inspect confirmation, fee rate and conflicts; wait when there is no urgency; then use wallet-supported RBF or CPFP only when appropriate.

Stop if the wallet reports database damage, missing keys, an unexpectedly huge fee or a destination you did not enter. Preserve backups and logs and seek support through independently verified channels before changing wallet files.

Visual recap

Diagnose before taking action

The safest action depends on whether the transaction was created, accepted and confirmed.

01

Wallet creates

02

Node accepts or rejects

03

Mempools relay

04

Miner selects

05

Block confirms

06

Wallet reconciles

Key takeaways

  • Failed creation, node rejection and delayed confirmation are different states.
  • An unconfirmed transaction is not automatically invalid.
  • Each node maintains its own mempool.
  • RBF and CPFP should be used through understood wallet features.
  • Never resend blindly or expose recovery secrets while troubleshooting.

Lesson recap

Check what you learned

Reveal each model answer, then honestly mark whether you understood it or need another review.

1 of 3

Recall

Why is it unsafe to create a second payment simply because the first is not visible on one explorer?

References

Further reading

Lesson progress

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