First 500 invoice numbers

INV-2026-00001, INV-2026-00002, INV-2026-00003, INV-2026-00004, INV-2026-00005, INV-2026-00006, INV-2026-00007, INV-2026-00008, INV-2026-00009, INV-2026-00010, INV-2026-00011, INV-2026-00012, INV-2026-00013, INV-2026-00014, INV-2026-00015, INV-2026-00016, INV-2026-00017, INV-2026-00018, INV-2026-00019, INV-2026-00020, INV-2026-00021, INV-2026-00022, INV-2026-00023, INV-2026-00024, INV-2026-00025, INV-2026-00026, INV-2026-00027, INV-2026-00028, INV-2026-00029, INV-2026-00030, INV-2026-00031, INV-2026-00032, INV-2026-00033, INV-2026-00034, INV-2026-00035, INV-2026-00036, INV-2026-00037, INV-2026-00038, INV-2026-00039, INV-2026-00040, INV-2026-00041, INV-2026-00042, INV-2026-00043, INV-2026-00044, INV-2026-00045, INV-2026-00046, INV-2026-00047, INV-2026-00048, INV-2026-00049, INV-2026-00050, INV-2026-00051, INV-2026-00052, INV-2026-00053, INV-2026-00054, INV-2026-00055, INV-2026-00056, INV-2026-00057, INV-2026-00058, INV-2026-00059, INV-2026-00060, INV-2026-00061, INV-2026-00062, INV-2026-00063, INV-2026-00064, INV-2026-00065, INV-2026-00066, INV-2026-00067, INV-2026-00068, INV-2026-00069, INV-2026-00070, INV-2026-00071, INV-2026-00072, INV-2026-00073, INV-2026-00074, INV-2026-00075, INV-2026-00076, INV-2026-00077, INV-2026-00078, INV-2026-00079, INV-2026-00080, INV-2026-00081, INV-2026-00082, INV-2026-00083, INV-2026-00084, INV-2026-00085, INV-2026-00086, INV-2026-00087, INV-2026-00088, INV-2026-00089, INV-2026-00090, INV-2026-00091, INV-2026-00092, INV-2026-00093, INV-2026-00094, INV-2026-00095, INV-2026-00096, INV-2026-00097, INV-2026-00098, INV-2026-00099, INV-2026-00100, INV-2026-00101, INV-2026-00102, INV-2026-00103, INV-2026-00104, INV-2026-00105, INV-2026-00106, INV-2026-00107, INV-2026-00108, INV-2026-00109, INV-2026-00110, INV-2026-00111, INV-2026-00112, INV-2026-00113, INV-2026-00114, INV-2026-00115, INV-2026-00116, INV-2026-00117, INV-2026-00118, INV-2026-00119, INV-2026-00120, INV-2026-00121, INV-2026-00122, INV-2026-00123, INV-2026-00124, INV-2026-00125, INV-2026-00126, INV-2026-00127, INV-2026-00128, INV-2026-00129, INV-2026-00130, INV-2026-00131, INV-2026-00132, INV-2026-00133, INV-2026-00134, INV-2026-00135, INV-2026-00136, INV-2026-00137, INV-2026-00138, INV-2026-00139, INV-2026-00140, INV-2026-00141, INV-2026-00142, INV-2026-00143, INV-2026-00144, INV-2026-00145, INV-2026-00146, INV-2026-00147, INV-2026-00148, INV-2026-00149, INV-2026-00150, INV-2026-00151, INV-2026-00152, INV-2026-00153, INV-2026-00154, INV-2026-00155, INV-2026-00156, INV-2026-00157, INV-2026-00158, INV-2026-00159, INV-2026-00160, INV-2026-00161, INV-2026-00162, INV-2026-00163, INV-2026-00164, INV-2026-00165, INV-2026-00166, INV-2026-00167, INV-2026-00168, INV-2026-00169, INV-2026-00170, INV-2026-00171, INV-2026-00172, INV-2026-00173, INV-2026-00174, INV-2026-00175, INV-2026-00176, INV-2026-00177, INV-2026-00178, INV-2026-00179, INV-2026-00180, INV-2026-00181, INV-2026-00182, INV-2026-00183, INV-2026-00184, INV-2026-00185, INV-2026-00186, INV-2026-00187, INV-2026-00188, INV-2026-00189, INV-2026-00190, INV-2026-00191, INV-2026-00192, INV-2026-00193, INV-2026-00194, INV-2026-00195, INV-2026-00196, INV-2026-00197, INV-2026-00198, INV-2026-00199, INV-2026-00200, INV-2026-00201, INV-2026-00202, INV-2026-00203, INV-2026-00204, INV-2026-00205, INV-2026-00206, INV-2026-00207, INV-2026-00208, INV-2026-00209, INV-2026-00210, INV-2026-00211, INV-2026-00212, INV-2026-00213, INV-2026-00214, INV-2026-00215, INV-2026-00216, INV-2026-00217, INV-2026-00218, INV-2026-00219, INV-2026-00220, INV-2026-00221, INV-2026-00222, INV-2026-00223, INV-2026-00224, INV-2026-00225, INV-2026-00226, INV-2026-00227, INV-2026-00228, INV-2026-00229, INV-2026-00230, INV-2026-00231, INV-2026-00232, INV-2026-00233, INV-2026-00234, INV-2026-00235, INV-2026-00236, INV-2026-00237, INV-2026-00238, INV-2026-00239, INV-2026-00240, INV-2026-00241, INV-2026-00242, INV-2026-00243, INV-2026-00244, INV-2026-00245, INV-2026-00246, INV-2026-00247, INV-2026-00248, INV-2026-00249, INV-2026-00250, INV-2026-00251, INV-2026-00252, INV-2026-00253, INV-2026-00254, INV-2026-00255, INV-2026-00256, INV-2026-00257, INV-2026-00258, INV-2026-00259, INV-2026-00260, INV-2026-00261, INV-2026-00262, INV-2026-00263, INV-2026-00264, INV-2026-00265, INV-2026-00266, INV-2026-00267, INV-2026-00268, INV-2026-00269, INV-2026-00270, INV-2026-00271, INV-2026-00272, INV-2026-00273, INV-2026-00274, INV-2026-00275, INV-2026-00276, INV-2026-00277, INV-2026-00278, INV-2026-00279, INV-2026-00280, INV-2026-00281, INV-2026-00282, INV-2026-00283, INV-2026-00284, INV-2026-00285, INV-2026-00286, INV-2026-00287, INV-2026-00288, INV-2026-00289, INV-2026-00290, INV-2026-00291, INV-2026-00292, INV-2026-00293, INV-2026-00294, INV-2026-00295, INV-2026-00296, INV-2026-00297, INV-2026-00298, INV-2026-00299, INV-2026-00300, INV-2026-00301, INV-2026-00302, INV-2026-00303, INV-2026-00304, INV-2026-00305, INV-2026-00306, INV-2026-00307, INV-2026-00308, INV-2026-00309, INV-2026-00310, INV-2026-00311, INV-2026-00312, INV-2026-00313, INV-2026-00314, INV-2026-00315, INV-2026-00316, INV-2026-00317, INV-2026-00318, INV-2026-00319, INV-2026-00320, INV-2026-00321, INV-2026-00322, INV-2026-00323, INV-2026-00324, INV-2026-00325, INV-2026-00326, INV-2026-00327, INV-2026-00328, INV-2026-00329, INV-2026-00330, INV-2026-00331, INV-2026-00332, INV-2026-00333, INV-2026-00334, INV-2026-00335, INV-2026-00336, INV-2026-00337, INV-2026-00338, INV-2026-00339, INV-2026-00340, INV-2026-00341, INV-2026-00342, INV-2026-00343, INV-2026-00344, INV-2026-00345, INV-2026-00346, INV-2026-00347, INV-2026-00348, INV-2026-00349, INV-2026-00350, INV-2026-00351, INV-2026-00352, INV-2026-00353, INV-2026-00354, INV-2026-00355, INV-2026-00356, INV-2026-00357, INV-2026-00358, INV-2026-00359, INV-2026-00360, INV-2026-00361, INV-2026-00362, INV-2026-00363, INV-2026-00364, INV-2026-00365, INV-2026-00366, INV-2026-00367, INV-2026-00368, INV-2026-00369, INV-2026-00370, INV-2026-00371, INV-2026-00372, INV-2026-00373, INV-2026-00374, INV-2026-00375, INV-2026-00376, INV-2026-00377, INV-2026-00378, INV-2026-00379, INV-2026-00380, INV-2026-00381, INV-2026-00382, INV-2026-00383, INV-2026-00384, INV-2026-00385, INV-2026-00386, INV-2026-00387, INV-2026-00388, INV-2026-00389, INV-2026-00390, INV-2026-00391, INV-2026-00392, INV-2026-00393, INV-2026-00394, INV-2026-00395, INV-2026-00396, INV-2026-00397, INV-2026-00398, INV-2026-00399, INV-2026-00400, INV-2026-00401, INV-2026-00402, INV-2026-00403, INV-2026-00404, INV-2026-00405, INV-2026-00406, INV-2026-00407, INV-2026-00408, INV-2026-00409, INV-2026-00410, INV-2026-00411, INV-2026-00412, INV-2026-00413, INV-2026-00414, INV-2026-00415, INV-2026-00416, INV-2026-00417, INV-2026-00418, INV-2026-00419, INV-2026-00420, INV-2026-00421, INV-2026-00422, INV-2026-00423, INV-2026-00424, INV-2026-00425, INV-2026-00426, INV-2026-00427, INV-2026-00428, INV-2026-00429, INV-2026-00430, INV-2026-00431, INV-2026-00432, INV-2026-00433, INV-2026-00434, INV-2026-00435, INV-2026-00436, INV-2026-00437, INV-2026-00438, INV-2026-00439, INV-2026-00440, INV-2026-00441, INV-2026-00442, INV-2026-00443, INV-2026-00444, INV-2026-00445, INV-2026-00446, INV-2026-00447, INV-2026-00448, INV-2026-00449, INV-2026-00450, INV-2026-00451, INV-2026-00452, INV-2026-00453, INV-2026-00454, INV-2026-00455, INV-2026-00456, INV-2026-00457, INV-2026-00458, INV-2026-00459, INV-2026-00460, INV-2026-00461, INV-2026-00462, INV-2026-00463, INV-2026-00464, INV-2026-00465, INV-2026-00466, INV-2026-00467, INV-2026-00468, INV-2026-00469, INV-2026-00470, INV-2026-00471, INV-2026-00472, INV-2026-00473, INV-2026-00474, INV-2026-00475, INV-2026-00476, INV-2026-00477, INV-2026-00478, INV-2026-00479, INV-2026-00480, INV-2026-00481, INV-2026-00482, INV-2026-00483, INV-2026-00484, INV-2026-00485, INV-2026-00486, INV-2026-00487, INV-2026-00488, INV-2026-00489, INV-2026-00490, INV-2026-00491, INV-2026-00492, INV-2026-00493, INV-2026-00494, INV-2026-00495, INV-2026-00496, INV-2026-00497, INV-2026-00498, INV-2026-00499, INV-2026-00500

500 references from "INV-{YYYY}-{SEQ:5}", counting up by one from 1. These are test fixtures: well-formed references that belong to no ledger and carry no tax significance.

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Pattern

Fields: {SEQ:5} zero-padded counter, {YYYY} and {YY} year, {MM} month, {DD} day, {Q} quarter, {N:4} random digits, {A:3} random letters, {X:6} random letters and digits. Write {{ and }} for literal braces.

Start the counter at

Any whole number up to 30 digits. Arithmetic here is arbitrary-precision, so continuing a series from 90071992547409910001 stays exact.

Counter step

Leave at 1 for a gapless series. A larger step deliberately leaves gaps, which is the opposite of what most tax rules want.

Year

Used by {YYYY} and {YY}. Taken as a parameter, never from the system clock, so the output never changes under you.

Month

Used by {MM} and, divided into thirds, by {Q}.

Day

Used by {DD}. Checked against the month and the Gregorian leap rule, so 29 February only works in a leap year.

Seed

Only matters if the pattern uses {N}, {A} or {X}. The same seed always gives the same random fields.

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Results

500 values

500 references from "INV-{YYYY}-{SEQ:5}", counting up by one from 1. These are test fixtures: well-formed references that belong to no ledger and carry no tax significance.

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Turn on JavaScript to style and download these numbers as an image. The values themselves are listed above.

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Drag a line straight onto the picture to place it — once placed, it stays exactly where you put it. Everything here is drawn into the download.

What are the first 500 invoice numbers?

The first 500 invoice numbers are:

About invoice numbers

The habit of giving every piece of paper a number belongs to double-entry bookkeeping, and the oldest surviving records of that practice are Italian. A ledger kept for Giovannino Farolfi & Company, a firm of Florentine merchants headquartered in Nîmes whose most important customer was the Archbishop of Arles, covers 1299–1300 and is the earliest surviving set of records in full double entry; the name of the merchant who kept it, Amatino Manucci, survives with it.

Luca Pacioli, a Franciscan friar and collaborator of Leonardo da Vinci, put the method into print. His Summa de arithmetica, geometria, proportioni et proportionalità (Venice, 1494) devotes a treatise — Particularis de computis et scripturis — to what he called the Venetian method: a memorandum, a journal and a ledger, with every entry cross-referenced between them. He is often called the father of accounting, and the careful version of the claim is that he was the first to publish a detailed description, not the first to write one: Benedetto Cotrugli, a Ragusan merchant and ambassador to Naples, had described double entry in a treatise composed in 1458 that went unprinted until 1573, by which time its printer had cut and garbled the relevant passages. What Pacioli insisted on was that entries be dated, ordered and traceable, because an account nobody can trace is an account nobody can audit. Werner Sombart's later claim that double-entry bookkeeping made modern capitalism possible has been argued over by economic historians ever since and is not a settled result.

Numbering became law much later. Article 226 of Council Directive 2006/112/EC, the EU VAT Directive, lists the details a VAT invoice must carry, and point (2) asks for "a sequential number, based on one or more series, which uniquely identifies the invoice". Member states wrote the rule into their own codes; Germany's Umsatzsteuergesetz, in §14(4), calls it a fortlaufende Nummer — a running number assigned once and only once. The purpose is completeness rather than tidiness. If a series has no gaps, a missing invoice is visible to anyone who counts, and a business cannot quietly drop a sale from its records. Whether a gap by itself invalidates a series is a question of national case law, not of the Directive, and several tax authorities now certify billing software instead of reconstructing sequences after the fact.

Key properties

Article 226(2) of Council Directive 2006/112/EC requires a VAT invoice to carry "a sequential number, based on one or more series, which uniquely identifies the invoice".
The phrase "based on one or more series" is what makes per-year or per-branch prefixes lawful: INV-2026-00001 and CN-2026-00001 are two series, each sequential within itself.
Nothing in the Directive fixes a format — the prefix, the separators, the field widths and the starting value are all the issuer’s choice.
Ledgers kept in full double entry survive from 1299–1300, nearly two centuries before Luca Pacioli published the first detailed printed description of the method in 1494.
The pattern fields are {SEQ:n} for the padded counter, {YYYY} and {YY} for the year, {MM}, {DD} and {Q} for month, day and quarter, {N:n} for random digits, {A:n} for random letters and {X:n} for random letters and digits.
The counter is held as an arbitrary-precision integer, so a series continued from 90071992547409910001 increments exactly; the same value in a double-precision number would round to the nearest representable integer.
Year, month and day are inputs rather than clock readings, so the same link renders the same references indefinitely.
A gapless series is an audit control, not a privacy measure: two invoices from the same series disclose how many were issued between them.

Other lengths

Sources

Double-entry bookkeeping — Wikipedia — CC BY-SA 4.0
MacTutor History of Mathematics — Luca Pacioli — CC BY-SA 4.0
Council Directive 2006/112/EC (the EU VAT Directive) — EUR-Lex — © European Union — reuse authorised under Decision 2011/833/EU
§14 Umsatzsteuergesetz (Ausstellung von Rechnungen) — Gesetze im Internet — Public domain — official work under §5 UrhG