C21i UK — when to file a Notification of Presentation for EIDR

C21i UK — definition and role in the CDS ecosystem

C21i is the electronic Notification of Presentation message used in the UK exclusively for imports settled under the EIDR (Entry in Declarant's Records) procedure — one of the two pillars of the CFSP (Customs Freight Simplified Procedures) authorisation, alongside SDP (Simplified Declaration Procedure). HMRC describes the mechanism in GOV.UK — Making a simplified frontier declaration: where an ordinary importer would file a full import declaration, an EIDR-authorised importer makes an entry in their own records and sends HMRC the NOP alone in the form of a C21i.

The letter "i" in the name C21i stands for "inventory" — it signals that the message relates to an entry in the declarant's inventory (their own customs records), rather than a standard import declaration. In practice C21i is a contextual message — without an active EIDR authorisation you have no legal basis to submit one. HMRC will reject it with an authorisation error.

The role of C21i is easiest to grasp alongside the other CDS messages: full declaration (H1) = the default option, SFD (Simplified Frontier Declaration) = a simplified border declaration with a mandatory later supplementary declaration, C21i = the NOP for EIDR — "the goods are at the border; we are doing the declaration in our own records".

C21 vs C21i — the distinction you must understand

The names are similar, but the mechanics are entirely different. C21 (without the "i") is the so-called Customs Clearance Request — a message used historically in CHIEF and now in CDS mainly for air cargo and consignments at inventory-linked ports, in situations where the shipment does not require a full import declaration (e.g. goods in movement, consignments relieved of duty below a threshold). C21 is not tied to any simplification authorisation — any importer or customs agent can file one, provided the technical conditions are met.

C21i is an entirely different beast: it is the EIDR message, which without a CFSP/EIDR authorisation is useless. In the CDS environment the two messages are separate declaration types with separate validation procedures. In the UK Trade Tariff: Volume 3 for CDS HMRC separates them at the level of the Declaration Type (Data Element 1/1) and the associated Additional Procedure Codes.

In practical terms for a UK importer this has one very concrete consequence: if your customs software or ERP is logging "C21" to HMRC but you are on EIDR — you are probably doing it wrong. You have to log a C21i citing the EIDR authorisation, not an ordinary C21. The EasyClearance Team has come across importers whose previous broker had for years been sending incorrect messages — everything worked from a logistics point of view, but the HMRC audit risk was serious.

When exactly must a C21i be filed

The obligation to file a C21i arises the moment an EIDR-authorised importer brings goods into the UK and chooses to settle them via the simplified route rather than a full import declaration. In GOV.UK — Apply to use simplified declarations for imports, HMRC describes the crucial moment in EIDR as the so-called pre-loading notification — notifying HMRC of the presence of the goods before they are loaded onto the means of transport bound for the UK.

In concrete terms: the C21i must be sent and accepted by HMRC before the moment at which the container/trailer/consignment is physically loaded onto the vessel/ferry/aircraft/lorry heading for the UK. Not "before arrival at the border", not "before entry into UK territory" — before loading. This is the key difference from SFD (which allows post-loading notification in some modes) and from a full declaration (which can be filed on an arrival basis).

When is a C21i not required: if an EIDR-authorised importer chooses, for a particular transaction, to file a full declaration (H1) or an SFD — they may. EIDR is a right, not an obligation for every consignment. But if the EIDR route is selected, the NOP in the form of a C21i becomes mandatory and the pre-loading timing is non-negotiable. A breach of the pre-loading timing is one of the most frequently cited causes of HMRC revoking a CFSP authorisation.

Who files a C21i — declarant vs customs agent

The responsible party is the declarant — the entity holding the EIDR authorisation. In the UK this is normally the importer itself (the goods owner with a UK EORI) or an entity acting on the basis of a direct customs representation from the importer. In its guidance on the CFSP authorisation, HMRC is clear — responsibility for EIDR compliance is not transferred to the customs agent.

A customs agent may physically submit the C21i on the importer's behalf, but only where:

• The importer holds an active CFSP/EIDR authorisation granted by HMRC (the authorisation number is cited in the declaration).
• The agent has written authority for direct representation from the importer.
• The agent files the declaration under the importer's EORI, not the agent's own (EIDR is unavailable under indirect representation).

That means that under the EIDR model a customs agent cannot simply "accept an instruction" the way they might with a standard clearance — they must have documented authority and must understand that any errors (wrong goods classification, missing entry in records, late NOP) count against the importer's compliance record, not the agent's. At the EasyClearance Team we treat the client's EIDR authorisation as an entry condition — before the first C21i submission we verify the currency of the authorisation number with HMRC and rewrite the client's SOP so that pre-loading cannot be skipped (trigger in the ERP, checkpoint in the workflow).

When exactly — pre-loading timing in practice

The critical moment is "before loading onto transport bound for the UK". In practice this means different things depending on the mode:

• Deep-sea container — NOP before the container is loaded onto the vessel at the origin port (e.g. Shanghai, Singapore, Rotterdam). In practice the forwarder provides the S/O and documents 48–72h before sailing — the customs agent must file the C21i within that window.
• RoRo lorry via Dover/Folkestone — NOP before the trailer is loaded onto the ferry at Calais/Coquelles. Typically this means sending the C21i at least 2–4h before the driver's planned arrival at the ferry gate.
• Air cargo to Heathrow/East Midlands — NOP before the consignment is loaded onto the aircraft at the origin airport. For fast intra-EU flights this can be a 1–2h window.
• Eurotunnel shuttle — NOP before the trailer boards the shuttle at Coquelles. Analogous to Dover.

HMRC does not publish a single universal "how many hours before" figure — the obligation is defined by the event (loading), not by the clock. That is why it is so important for the client's ERP to generate the C21i trigger the moment the booking is confirmed and the loading plan is known, rather than on arrival in the UK. The latter is simply too late.

How to file a C21i — two CDS channels

HMRC makes two technical channels available for sending a C21i, both through the CDS (Customs Declaration Service):

Channel 1: CDS direct — customs broker software. The most common option for UK firms without an in-house IT team. The customs agent logs into their software (e.g. Descartes, Sequoia, CargoWise One, BCP CustomsDesk, MIC Customs Solutions), completes the declaration form with type "C21i", enters the importer's EORI, the EIDR authorisation number, the UCR, the location code (DE 5/23) and the transport details. The software transmits the message in CDS XML to the HMRC gateway, HMRC validates it and returns an MRN with an Accepted status. The whole process takes anywhere from 30 seconds to a few minutes depending on the load on the HMRC gateway.

Channel 2: CDS API — integration with the client's ERP. For importers with large volumes (100+ C21i per month), direct integration with the CDS API pays off. HMRC publishes the technical documentation at the HMRC Developer Hub — Customs Declarations API: a REST API for filing declarations, checking status, retrieving MRNs and subscribing to notifications. The client's ERP generates the C21i automatically the moment a booking is created — no human involvement required. This is the model preferred by e-commerce operations with regular imports into the UK.

The EasyClearance Team supports clients on both channels — small and mid-sized importers via our software (channel 1), larger operations via implementation support for CDS API integration into their ERP (channel 2). We go deeper into the difference between these models and when it is worth moving to the API in the pillar article CFSP — UK Customs Freight Simplified Procedures.

C21i data requirements — checklist before submission

Before the customs agent (or the ERP system) sends a C21i to CDS, the following data must be complete — any missing item causes an HMRC rejection:

1. Importer EORI (with an active EIDR authorisation) — checked against the HMRC EORI validator database.
2. EIDR authorisation number — entered in the relevant declaration field (Data Element 3/39).
3. UCR or DUCR — Unique Consignment Reference linking the consignment to the logistics booking.
4. Goods location code (DE 5/23) — Goods Location Code from the official HMRC list; it must match the actual port/terminal of entry.
5. Transport code — vessel/flight/trailer/truck identifier from the booking.
6. Manifest / bill of lading / AWB number — the transport document number.
7. Goods description — a concise commodity description (not as detailed as in H1).
8. Gross mass — in kilograms.
9. Additional Procedure Codes — where applicable (rarely in a C21i).

The full list of Data Elements for a C21i is in the CDS Volume 3 Import Declaration Completion Guide, in the section for Declaration Type "C21i". The EasyClearance Team maintains an up-to-date C21i checklist as part of the SOP for every EIDR client — this is the sort of area where a single wrong field in the 100th message of the month generates 100 rejections in a single day.

C21i vs SFD — when to choose which mode

A CFSP-authorised importer often has a choice between two simplified routes: SFD (Simplified Frontier Declaration, related to SDP) or EIDR + C21i. They are not equivalent — they differ on timing, data scope and operational load.

SFD is a simplified border declaration with a minimal set of Data Elements, filed in CDS before or at the point of arrival and closed out with a full supplementary declaration. A customs agent sees it as a "smaller H1". C21i + EIDR is a completely different model — the goods data lives in the importer's records, CDS receives only an NOP of presence, and the full declaration comes later as a Supplementary Declaration (usually monthly).

A simple rule of thumb: if the importer has well-designed in-house customs records and wants maximum flexibility (including cash flow via deferred VAT), EIDR + C21i wins. If the importer prefers every transaction visible in CDS from the start and does not want to invest in a records system — SFD is simpler. We go into the detailed comparison and the authorisation conditions in the companion article Simplified Frontier Declaration (SFD) UK.

After the C21i — Supplementary Declaration and the entry in records

Filing a C21i does not close the EIDR cycle — it is only the first step. After NOP acceptance the declarant must carry out two further obligations:

Step 1 — entry in the EIDR records. At the "tax point" (normally the physical receipt of the goods in the UK) the declarant makes an entry in their internal customs records containing all the data that would sit in a full H1 declaration: tariff classification, origin, customs value, VAT, duty, restrictions. This entry is the foundation of EIDR compliance — in an audit HMRC looks at the records, not the C21is themselves. The quality requirements for the records are set out in GOV.UK — Records for CFSP.

Step 2 — Supplementary Declaration. Within the deadline set by the authorisation (usually by the 10th of the month following the month in which the tax point occurred), the declarant files to CDS a full Supplementary Declaration, aggregated or per transaction. That is what closes the fiscal cycle — accounting for duty and VAT (or deferring VAT via PVA) and generating the C88/H1 as the final document.

In full, the EIDR cycle for one consignment is: C21i (pre-loading) → arrival → entry in records (tax point) → Supplementary Declaration (monthly) → cycle closed. The most common error made by importers starting out with EIDR is forgetting step 1 — the C21i goes out correctly, the Supplementary Declaration is filed, but the records do not tie back to the declarations, and in an audit it turns out the evidence is missing. For EIDR clients, the EasyClearance Team designs the accounting flow for records too (not just the C21i), so that all three links sit in the same system and can be verified.

The most common C21i errors and how to avoid them

After hundreds of C21is filed for EIDR clients, we have a short list of typical problems:

• Late NOP (post-loading) — C21i sent after the container/trailer has already moved. Formally that is an authorisation incident. Fix: ERP trigger at the confirmed-booking moment, not at arrival.
• Wrong DE 5/23 location code — the importer expects Felixstowe, the vessel turns up at London Gateway, the C21i carries the old code. Fix: sync with the shipping line 24h before sailing.
• EORI without an active EIDR authorisation — authorisation expired, suspended, or issued to a different entity in the group. Fix: monthly verification of the authorisation number with HMRC.
• UCR that does not match the manifest — especially with groupage. Causes issues at release in inventory-linked ports. Fix: coordinate the UCR with the forwarder before the first shipment.
• Missing Additional Procedure Codes for licensed goods — e.g. excise goods, products of animal origin, dual-use items. EIDR does not waive licensing procedures. Fix: check the goods category before deciding on EIDR.

Each of these errors is detectable either at submission in CDS (HMRC rejects the message) or later in an audit. The EasyClearance Team reviews the first 20–30 submissions of every new EIDR client "by hand" to catch any systemic errors at ERP level before they become a habit.

How the EasyClearance Team supports EIDR clients — 2026 model

Our practice for importers with a CFSP/EIDR authorisation:

1. Onboarding — authorisation audit. We verify the authorisation number with HMRC, scan the client-specific conditions (e.g. goods category restrictions, value caps) and record them as SOP.
2. C21i flow setup. We map the client's ERP fields to the C21i Data Elements, set the pre-loading trigger, and test the first submissions in the CDS test environment.
3. Production — 30 days under close review. In the first month every C21i submission is checked by hand by an EasyClearance Team operator. We catch systemic errors.
4. Run — monitoring and reporting. Weekly C21i acceptance-rate report, monthly consistency report C21i ↔ records ↔ Supplementary.
5. HMRC audit — end-to-end support. At a CFSP audit (typically every 2–3 years) we provide the client with the full pack of documents and join the HMRC meetings as customs agent.

Our per-declaration rates are out in the open — they are published in the EasyClearance 2026 pricing (Standard, Business, Enterprise), separately for imports and for C21i handling under CFSP/EIDR. C21i rates are priced per declaration, and CFSP authorisation configuration is priced separately based on the setup scope.

Related topics in the EasyClearance Knowledge Base

C21i belongs to the wider CFSP ecosystem — if you are just getting started with UK simplifications, it is worth reading this alongside:

• CFSP — UK Customs Freight Simplified Procedures — the cluster pillar, an overview of SDP and EIDR as the two authorisation pillars.
• CFSP — when it is worth it — a decision-led take: who benefits from CFSP and who does not.
• Simplified Frontier Declaration (SFD) UK — the EIDR alternative in border-minimum-data mode.

Official sources

• GOV.UK: Making a simplified frontier declaration — GOV.UK / HMRC, 2026
• GOV.UK: Apply to use simplified declarations for imports (CFSP) — GOV.UK / HMRC, 2026
• GOV.UK: Records you must keep for CFSP — GOV.UK / HMRC, 2026
• GOV.UK: UK Trade Tariff Volume 3 for CDS — GOV.UK / HMRC, 2026
• GOV.UK: CDS Volume 3 — Import Declaration Completion Guide — GOV.UK / HMRC, 2026
• HMRC Developer Hub: Customs Declarations API — HMRC Developer Hub, 2026

Frequently asked questions (FAQ)

What is a C21i in the UK?

C21i is the electronic Notification of Presentation (NOP) message filed in CDS exclusively for imports settled under the EIDR (Entry in Declarant's Records) procedure within a CFSP authorisation. The letter "i" in the name stands for "inventory" — the message tells HMRC that the goods have reached the UK border and that the full data sits in the importer's records, not in a CDS declaration. C21i replaces the full import declaration at the point of arrival, and only later (typically monthly) does the declarant file a Supplementary Declaration to close the fiscal cycle.

What is the difference between C21 and C21i?

C21 (without the "i") is a Customs Clearance Request — a general message used mainly for air cargo and inventory-linked consignments in situations where a full declaration is not required (e.g. goods relieved of duty, transit movements). C21 does not require a CFSP authorisation. C21i is the dedicated EIDR message — without an active CFSP/EIDR authorisation it is useless and HMRC will reject it with an authorisation error. Both are separate declaration types in CDS (Declaration Type in Data Element 1/1) with separate validation procedures.

Who files a C21i?

The responsible party is the declarant holding the CFSP/EIDR authorisation — usually the importer itself (the goods owner with a UK EORI). A customs agent may physically submit a C21i on the importer's behalf, but only under direct representation and under the importer's EORI, not the agent's. EIDR is unavailable under indirect representation. Responsibility for compliance (correct NOP, records, Supplementary) remains with the declarant regardless of who technically sends the message.

When must a C21i be filed — before arrival or before loading?

The C21i must be sent and accepted by HMRC before the moment at which the goods are physically loaded onto the means of transport bound for the UK — not before arrival at the UK border, but before loading at the origin port (Shanghai, Rotterdam, Calais, etc.). This is a hard HMRC rule, known as the pre-loading notification. A breach (late NOP, post-loading) is one of the most frequently cited causes of CFSP authorisation being revoked. In practice it means a trigger in the client's ERP at the confirmed-booking moment, not on arrival.

How do I send a C21i — via CDS or via the API?

HMRC provides two technical channels, both through CDS (Customs Declaration Service). Channel 1: CDS direct — a customs agent uses their software (Descartes, Sequoia, CargoWise One, MIC, BCP CustomsDesk) to send the message in CDS XML. Channel 2: CDS API — direct integration between the client's ERP and the HMRC Customs Declarations API (REST). The API channel is preferred for large volumes (100+ C21i per month); direct via customs broker software is fine for smaller importers. Both return an MRN and an Accepted/Rejected status.

What happens after the C21i is submitted?

C21i is the first step in a three-part EIDR cycle: (1) file the C21i before loading; (2) make an entry in the declarant's internal customs records at the tax point (physical receipt of the goods in the UK) containing the full data — classification, origin, customs value, duty, VAT; (3) file a Supplementary Declaration to CDS within the deadline set by the authorisation (usually by the 10th of the month following the month of the tax point). Only the Supplementary Declaration closes the fiscal cycle and generates the C88/H1. A break in any of these three links is a risk of the CFSP authorisation being revoked at an HMRC audit.