specification/protocol/network/messages/reject.md

<div class="cwikmeta">{
"title":"REJECT",
"related":["/protocol"]
}</div>

# Response: Reject ("reject")

Notifies peer that a received message is invalid.

## Message Format

| Field | Length | Format | Description |
|--|--|--|--|
| rejected message type | variable | [variable length string](/protocol/formats/variable-length-string) | The [command string](/protocol/network/messages#command-string) of the message that is being rejected (e.g. "tx"). |
| rejection code | 1 byte | [rejection code](#rejection-codes) | A code indicating why the message was rejected. |
| rejection reason* | variable | [variable length string](/protocol/formats/variable-length-string) | A description of why the message was rejected. |

 \* *rejection reason* is a string providing a human language explanation of the reason the message was rejected.  This string is subject to change so client software **SHOULD NOT** use it programmatically.

#### Rejection Codes

|    Name    | Value | Response To |  Description |
|-------------|-------|---------------|-----------|
| REJECT_MALFORMED | 0x01 | any | Message cannot be deserialized. |
| REJECT_INVALID | 0x10 | BLOCK, TX, FILTERSIZEXTHIN | Block or transaction is invalid, or xthin filter size is too small | 
| REJECT_OBSOLETE | 0x11 | VERSION | This node no longer supports your client protocol version |
| REJECT_DUPLICATE | 0x12 | unused | |
| REJECT_NONSTANDARD | 0x40 | TX | Transaction is [non-standard](/protocol/blockchain/transaction-validation/network-level-validation-rules#standard-transactions), or not final as per [BIP68](/protocol/forks/bip-0068). |
| REJECT_DUST  | 0x41 | TX | Transaction has an output that is too small. |
| REJECT_INSUFFICIENTFEE | 0x42 | TX | Transaction does not pay enough in fees to be relayed. |
| REJECT_CHECKPOINT | 0x43 | unused | |