[#PaysForRBF]
= PaysForRBF
:mrdocs:

The replacement transaction must pay more fees than the original transactions. The additional fees must pay for the replacement's bandwidth at or above the incremental relay feerate.

== Synopsis

Declared in `<policy/rbf.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
std::optional<std::string>
PaysForRBF(
    xref:CAmount.adoc[CAmount] original_fees,
    xref:CAmount.adoc[CAmount] replacement_fees,
    size_t replacement_vsize,
    xref:CFeeRate.adoc[CFeeRate] relay_fee,
    xref:Txid.adoc[Txid] const& txid);
----

== Return Value

error string if fees are insufficient, otherwise std::nullopt.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *original_fees* [in]
| Total modified fees of original transaction(s).
| *replacement_fees* [in]
| Total modified fees of replacement transaction(s).
| *replacement_vsize* [in]
| Total virtual size of replacement transaction(s).
| *relay_fee* [in]
| The node's minimum feerate for transaction relay.
| *txid* [in]
| Transaction ID, included in the error message if violation occurs.
|===


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