An S10 identifier has 13 characters. The final country code identifies the issuing authority, while destination routing and customs information are separate.
Field explanation · 01
Service indicator · positions 1–2
On this sample: R / RT
Documented field / data example
RTRT falls within the documented RA–RZ registered letter-post indicator range.
Check before using
The indicator describes a postal product family, not a universal delivery-time commitment. RZ requires bilateral agreement.
Official reference: Identification of postal items – 13-character identifier
↑ Back to field directoryField explanation · 02
Serial number · positions 3–10
On this sample: RT011231107HK
Documented field / data example
01123110The serial number occupies eight numeric positions inside the complete identifier.
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The serial alone is not the complete 13-character tracking identifier.
Official reference: Identification of postal items – 13-character identifier
↑ Back to field directoryField explanation · 03
Check digit · position 11
Documented field / data example
7Position 11 is the S10 check digit.
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A valid check digit verifies identifier structure, not shipment acceptance, ownership or delivery.
Official reference: Identification of postal items – 13-character identifier · upu standards
↑ Back to field directoryField explanation · 04
Issuing-authority country · positions 12–13
On this sample: HK
Documented field / data example
HKThe suffix is the ISO country code under whose authority the identifier was issued.
Check before using
It is not a destination-country routing field; read the destination address separately.
Official reference: Identification of postal items – 13-character identifier
↑ Back to field directoryField explanation · 05
Account information
Documented field / data example
[NOT ENCODED IN S10 STRUCTURE]The four S10 components do not include a billing-account field.
Check before using
Verify postage and customer-account information elsewhere in the postal shipment record.
Official reference: Identification of postal items – 13-character identifier
↑ Back to field directoryField explanation · 06
Customs declaration
On this sample: CN22
Documented field / data example
CN22 · CD · HKD50.00This specimen integrates a CN22 customs declaration with the registered-item label. Reconcile the category, contents, weight, declared value and signature with the shipment record.
Check before using
The S10 format alone does not establish contents, declared value or customs clearance.
Official reference: Identification of postal items – 13-character identifier
↑ Back to field directoryField explanation · 07
Signature instruction
On this sample: Signature required
Documented field / data example
Signature requiredThe CN04 area includes an explicit signature-required instruction.
Check before using
The signature instruction is printed outside the 13-character S10 identifier. It does not prove a signature was collected, establish live delivery status or mean that the RT or HK components encode a signature result. Check the issued label and applicable service conditions.
Official reference: Identification of postal items – 13-character identifier
↑ Back to field directoryField explanation · 08
Additional non-S10 barcode
On this sample: Additional non-S10 barcode
Documented field / data example
Additional non-S10 barcodeThe source explains that a second non-S10 barcode can coexist with the S10 identifier. It must not be mistaken for a second S10 tracking number.
Check before using
The additional barcode is not a second S10 tracking identifier. Its presence alone does not establish a decoded payload, account, service code or accepted live shipment. Do not substitute it for RT011231107HK without documentation for that barcode and workflow.
Official reference: Identification of postal items – 13-character identifier
↑ Back to field directoryField explanation · 09
Actual destination
On this sample: Melville SK S0A 2P0 CANADA
Documented field / data example
Melville SK S0A 2P0 CANADAThe destination address supplies routing context. The HK suffix in the S10 number identifies the issuing authority.
Check before using
Canada is the destination in this illustrated address; HK in the S10 identifier is the issuing authority. The address does not establish an internal depot or route token, actual transport mode, current booking or shipment status. Preserve the source redactions rather than reconstructing masked address details.
Official reference: Identification of postal items – 13-character identifier
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