Search for how to decode a Vietnamese citizen ID and you will find the same structure everywhere: province of birth registration, century, sex, year of birth, then a random sequence. Hanoi is 001, Long An is 080.
That decode had a legal basis until 1 July 2024. It does not have one now, and the pages teaching it include a provincial police portal and the government's own policy site.
What used to be true
Decree 137/2015 set out the structure in an article devoted to it:
"Điều 13. Cấu trúc số định danh cá nhân — Số định danh cá nhân là dãy số tự nhiên gồm 12 số, có cấu trúc gồm 6 số là mã thế kỷ sinh, mã giới tính, mã năm sinh của công dân, mã tỉnh, thành phố trực thuộc trung ương hoặc mã quốc gia nơi công dân đăng ký khai sinh và 6 số là khoảng số ngẫu nhiên."
The twelve digits comprised six that encoded the holder's birth century, sex, birth year and province of birth registration, plus six random digits. The province code table itself lived in a Ministry of Public Security circular.
What happened on 1 July 2024
Three things, on the same day.
The decree was expressly repealed. Decree 70/2024, article 37(2):
"Nghị định số 137/2015/NĐ-CP ngày 31 tháng 12 năm 2015 … hết hiệu lực kể từ ngày Nghị định này có hiệu lực thi hành."
The circular carrying the province codes lapsed on the same date, taking the lookup table with it.
And the replacing law did not restore the structure. The Identification Law 2023, article 12, describes the number only as "dãy số tự nhiên gồm 12 chữ số" — a sequence of twelve natural digits — and provides no further specification. Its clause 4 delegates something narrower than people assume:
"Chính phủ quy định việc xác lập, hủy, xác lập lại số định danh cá nhân của công dân Việt Nam."
The clause covers the number's establishment, cancellation and re-establishment. Not its structure. And the decree written under that delegation, article 11, is procedural throughout — how a number is assigned, cancelled and reassigned — with no layout at all.
The absence is checkable
This is the kind of claim that is easy to assert and easy to test, so we tested it. Searching the full published text of the 2023 Law:
| Term | Meaning | Occurrences |
|---|---|---|
số định danh cá nhân | personal identification number | 24 — the control |
cấu trúc | structure | 0 |
mã tỉnh | province code | 0 |
mã thế kỷ | century code | 0 |
mã giới tính | sex code | 0 |
⚠️ The control row is the important one. A search returning zero proves nothing unless you also confirm you are searching the right document — a page that fails to load returns zero for everything. The subject term appears 24 times, so the zeros are real absences rather than a failed fetch.
Who is still teaching it
A provincial police portal published the decode in March 2025 — nine months after the change — with Hanoi = 001 and Long An = 080 as worked examples, and cited article 12 of the new Law as its authority. Article 12 is the one quoted above, which says twelve digits and stops.
The government's own policy portal carries the same explanation, correctly citing Decree 137/2015 and a 2016 circular. Both instruments are dead. The citation is accurate about where the rule came from and silent about the fact that it went.
And the codes themselves have rotted
There is a second layer. Vietnam reorganised its provinces in 2025, reducing 63 units to 34. Eleven were unchanged and the rest were merged.
63 − 11 = 52 old province codes that name a unit which no longer exists
11 + 23 merged units = 34So even taken on its own terms, the decode now maps most of its inputs to administrative units that were dissolved. A number issued in 2019 still contains whatever digits it was issued with; what changed is that the table translating them describes a country that has been redrawn.
What this does not mean
⚠️ It does not mean the digits are random now. Numbers issued under the old decree were presumably generated to that layout, and nothing about a repeal reaches back and reshuffles them. If you decode an existing number you may well get the right province.
The claim here is about legal authority, not arithmetic. No published rule now defines the number's structure, so the ministry is not obliged to keep following the old pattern, and you cannot tell from a number itself whether it was issued before or after the change. A decode that works is not the same as a decode you are entitled to rely on.
It does not mean the police portal is being careless in some unusual way, either. This is what happens when a widely known rule is removed rather than replaced: nothing generates a correction, because nothing announced a new answer.
What to do about it
If you are building anything that infers meaning from a Vietnamese ID number, such as a birth province, birth year or sex, stop. It is inference from a repealed rule against a province table that no longer matches the map, and the failure will be silent and demographically skewed.
If you are validating rather than decoding, validate what the law actually specifies: twelve digits. Anything stricter is enforcing a rule that no longer exists, and will start rejecting valid numbers the moment issuance stops following the old pattern.
And if you hold Vietnamese ID numbers in a system, treat them as opaque identifiers. That is now not merely good practice but an accurate description of their legal status.
Where this comes from, and what will date it
The repealed structure is quoted from article 13 of Decree 137/2015. The repeal is quoted from article 37(2) of Decree 70/2024. The twelve-digit description and the delegation wording are quoted from article 12 of Identification Law 26/2023, and the procedural replacement from article 11 of Decree 70/2024. The term counts in the table were run here against the published text of that Law, with the control described above.
⚠️ There are three limits to this. The province reorganisation figures are arithmetic on a widely reported 63-to-34 reduction; we have not independently verified which eleven units were unchanged, and the composition is relayed rather than checked. We have described what the instruments say, not what the ministry's issuance system does internally — it may well still follow the old layout. And Vietnamese legal publishing is layered, so a later decree could amend the 2024 one; the version we read carries amendment annotations, none of them touching the article that would restore a structure.
This dates the moment any instrument specifies a layout again, which would be a clean and welcome ending. It does not date through the pages that teach the old decode being corrected, because that is not how this kind of thing usually ends: the explanation outlives the rule, quietly, for as long as it keeps producing plausible answers.
