Item related to RCK Entry is Ineligible or RCK Entry is Improper
Category: Check conversion & RCK Initiated by: RDFI
Read reinitiation conditions and source →Applies to (SEC scope)
RCK
camt.053 mapping
Not mapped
Nacha's definition
A RCK Entry considered to be ineligible or improper.
Verbatim from Nacha — ISO 20022 Guide to Mapping U.S. ACH Return Items and Notifications of Change, August 2023, Version 2.01 (Table 1, return reason codes) (return reason code table). Applies to: RCK.
Reinitiation conditions
Nacha includes R51 in the unauthorized-return-rate group, but the public pages reviewed do not say that this classification alone invokes the separate prohibition on reinitiating a debit returned as unauthorized. They also do not establish a permitted way to re-present an RCK item returned as ineligible or improper. Confirm the governing Rules with your ODFI before any further entry.
Treat further ACH presentment as closed until your ODFI confirms otherwise against the current Operating Rules, which are what govern.
How it appears in an ISO 20022 statement
Nacha's mapping guide marks this code as not currently supported or mapped for camt.053 (footnote 1): it applies to Standard Entry Class codes or flows the guide does not cover, so it has no published ISO 20022 reason-code mapping.
Return time frame
Nacha includes R51 in its unauthorized entry return rate calculation. That rate category alone does not establish R51's return deadline; the code-specific time frame is in the Nacha Operating Rules and is not stated on the public pages used here.
Nacha counts this code toward an Originator's unauthorized entry return rate, whose threshold Nacha set at 0.5 percent. Each return under this code moves that ratio for your ODFI, independently of the money involved.
What an operator does next
The RCK re-presentment was ineligible or improper, so start with RCK eligibility screening. Nacha includes R51 in its unauthorized-return-rate calculation, but that inclusion alone does not establish a reinitiation ban for this item. The public pages reviewed do not establish a permitted R51 re-presentment route. PaymentBrief's guidance is to hold further ACH presentment until your ODFI confirms the applicable Rules and next step.
PaymentBrief guidance, not Nacha text. Your ODFI's procedures and the current Nacha Operating Rules govern.
Where this comes up on PaymentBrief
Sources for this code
- Nacha — ISO 20022 Guide to Mapping U.S. ACH Return Items and Notifications of Change, August 2023, Version 2.01 (Table 1, return reason codes) — retrieved 2026-09-06
- Nacha — rule page 'ACH Network Risk and Enforcement Topics' (unauthorized return rate threshold; reinitiation of entries) — retrieved 2026-09-06