National Insurance category letters

What each National Insurance category letter means: which employer relief and which employee rate class the letter selects.

Category letter	Employer relief	Employee class	Employee group
A	Standard	Standard	All employees apart from those in groups B, C, H, J, M, V and Z in this table
B	Standard	Married women reduced	Married women and widows who have a certificate of election form showing they're entitled to pay reduced National Insurance
C	Standard	Over state pension age	Employees over the State Pension age
H	Apprentice under 25	Standard	Apprentices under 25
J	Standard	Deferred	Employees who can defer National Insurance because they're already paying it in another job
M	Under 21	Standard	Employees under 21
V	Veteran	Standard	Employees who are working in their first job since leaving the armed forces (veterans)
Z	Under 21	Deferred	Employees under 21 who can defer National Insurance because they're already paying it in another job
F	Freeport	Standard	All employees who work in a special tax site within a Freeport, apart from those in groups I, L, and S in this table
I	Freeport	Married women reduced	Married women and widows working in a special tax site within a Freeport who have a certificate of election form showing they're entitled to pay reduced National Insurance
L	Freeport	Deferred	Employees who work in a special tax site within a Freeport and can defer National Insurance because they're already paying it in another job
S	Freeport	Over state pension age	Employees who work in a special tax site within a Freeport and are over the State Pension age
N	Investment zone	Standard	All employees who work in a special tax site within an Investment Zone, apart from those in groups E, D and K in this table
E	Investment zone	Married women reduced	Married women and widows working in a special tax site within an Investment Zone who have a certificate of election form showing they're entitled to pay reduced National Insurance
D	Investment zone	Deferred	Employees who work in a special tax site within an Investment Zone and can defer National Insurance because they're already paying it in another job
K	Investment zone	Over state pension age	Employees who work in a special tax site within an Investment Zone and are over State Pension age
X	No liability	No liability	employees who do not have to pay National Insurance, for example because they're under 16

Corroborated Administrative rate Great Britain in force since 2026-04-06

Checked against its sources: administering authority verified 2026-09-15·guidance verified 2026-09-21

Scope: A LOOKUP, not a table of numbers: each letter resolves to two codes, and the thresholds and percentages a code names are the existing records (National Insurance: secondary threshold (employers), .ust, .aust, .veterans_ust, .freeport_ust, .primary_threshold, .employee_main_rate, .employee_additional_rate, .married_women_reduced_rate, .employer_secondary_rate); a second copy of a threshold here would be the drift ADR-0013 §3 forbids. The codes are read from HMRC's own "Employee group" description of each letter and checked against the shape of the contribution tables on both pages (letters sharing a code share a rate row). Letter X (no liability, for example under 16s) is stated in prose on HMRC's page and on no rates table. HMRC's page dates its tables for the tax year 6 April 2026 to 5 April 2027 and states no earlier date for the letters; the Freeport letters (2022), the Investment Zone letters (2024) and V (2021) predate it, so this value says which letters are in use from 6 April 2026 and nothing about when each was introduced. No figure_ref output yet: a figure_ref must resolve on every entry, and neither an investment-zone upper secondary threshold (refused 2026-09-14, NICA 2022 s. 8 as archived names no investment zone) nor any threshold for X exists to point at. Employees who could carry more than one letter take the one HMRC's guidance directs, which this record does not decide.

Current sources

Source A · Administering authorityhttps://www.gov.uk/api/content/national-insurance-rates-letters (HMRC, "National Insurance rates and categories", part "Category letters": the three "Category letter / Employee group" tables — A, B, C, H, J, M, V, Z; Freeport F, I, L, S; Investment Zone N, E, D, K — and the "Category letter X" paragraph; the contribution tables in part "Contribution rates" list the same sixteen rated letters — every letter but X — "from 6 April 2026 to 5 April 2027")

retrieved 2026-09-15

Source B · Official guidancehttps://www.gov.uk/guidance/rates-and-thresholds-for-employers-2026-to-2027 ("Class 1 National Insurance rates": the employee and employer contribution tables list the same sixteen rated letters, 12 of them with HMRC's own gloss — "D (Investment Zone - deferment)", "E (Investment Zone - married women and widows reduced rate)", "F (Freeport)", "H (apprentice under 25)", "I (Freeport - married women and widows reduced rate)", "K (Investment Zone - state pensioner)", "L (Freeport - deferment)", "M (under 21)", "N (Investment Zone)", "S (Freeport - state pensioner)", "V (veteran)", "Z (under 21 - deferment)" — and letter X, which carries no rate, appears on no rates table)

retrieved 2026-07-29

History

Value

From

Status

Sources

Show table (17 rows)

Category letter	Employer relief	Employee class	Employee group
A	Standard	Standard	All employees apart from those in groups B, C, H, J, M, V and Z in this table
B	Standard	Married women reduced	Married women and widows who have a certificate of election form showing they're entitled to pay reduced National Insurance
C	Standard	Over state pension age	Employees over the State Pension age
H	Apprentice under 25	Standard	Apprentices under 25
J	Standard	Deferred	Employees who can defer National Insurance because they're already paying it in another job
M	Under 21	Standard	Employees under 21
V	Veteran	Standard	Employees who are working in their first job since leaving the armed forces (veterans)
Z	Under 21	Deferred	Employees under 21 who can defer National Insurance because they're already paying it in another job
F	Freeport	Standard	All employees who work in a special tax site within a Freeport, apart from those in groups I, L, and S in this table
I	Freeport	Married women reduced	Married women and widows working in a special tax site within a Freeport who have a certificate of election form showing they're entitled to pay reduced National Insurance
L	Freeport	Deferred	Employees who work in a special tax site within a Freeport and can defer National Insurance because they're already paying it in another job
S	Freeport	Over state pension age	Employees who work in a special tax site within a Freeport and are over the State Pension age
N	Investment zone	Standard	All employees who work in a special tax site within an Investment Zone, apart from those in groups E, D and K in this table
E	Investment zone	Married women reduced	Married women and widows working in a special tax site within an Investment Zone who have a certificate of election form showing they're entitled to pay reduced National Insurance
D	Investment zone	Deferred	Employees who work in a special tax site within an Investment Zone and can defer National Insurance because they're already paying it in another job
K	Investment zone	Over state pension age	Employees who work in a special tax site within an Investment Zone and are over State Pension age
X	No liability	No liability	employees who do not have to pay National Insurance, for example because they're under 16

2026-04-06

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Corroborated

Receipt

Everything above is reproducible and independently checkable — no trust in this site required (how verification works).

Figure ID: employment.ni.category_letter_matrix
Name in the API: National Insurance category letters: relief class by letter
Record fields (source type · unit · jurisdiction · status): administrative·ni_relief_class·GB·corroborated
Record hash (canonical JSON, SHA-256): sha256:cc19b1cd30409c801d4b4e2ee0f4d850a5ef3d79702549efae14805b12ce55c9
Source snapshots (SHA-256): Administering authority: sha256:621f365153fc9ccc3380e8cd8a3131118bcfe01339cfbd05538760e98804ad11; Official guidance: sha256:2b130359261b54fc8f27f3e53cade20f559a6035397c2e3845de72e21ea4eede
Listed in the signed manifest: release 3.0.0 manifest · record_hashes["employment.ni.category_letter_matrix"]
Machine-readable record: /v1/figures/employment.ni.category_letter_matrix · current only: /v1/figures/employment.ni.category_letter_matrix/current

Compiler's notes

An administrative table (D23(c)): HMRC is the administering authority and its own guidance page is the A-document, hashed in the receipt and re-read by this script. Every letter is read from the page's "Category letter / Employee group" tables (X from its paragraph) and refused if the page's set differs from the script's; each code is refused unless the words it is read from are in that letter's description ("under 21", "Apprentices under 25", "(veterans)", "special tax site within a Freeport", "... within an Investment Zone", "Married women and widows" with "reduced National Insurance", "defer National Insurance", "State Pension age", "do not have to pay National Insurance"), standard being the absence of every other code's words on that side. The employers' rates-and-thresholds page is the B side: it prints the same sixteen rated letters with HMRC's own bracketed glosses, each checked against the codes, so the value is corroborated; X is on no second page. The value is dated from the sentence the page dates its tables with, and the script refuses when that sentence goes.