FBR Invoice Number Rules 2026: Format, Serial Numbers and Can You Restart at 1?
Section 23 requires a serially numbered tax invoice. Here is the invoice number format FBR accepts, why error 0088 fires, and if you can restart at 1.
What this guide tells you, in plain words
Every FBR digital invoice carries two numbers, not one. One you choose. One FBR gives you.
This guide explains the number you choose: what the law demands, what shape FBR's system accepts, whether you may start again at 1 in July, and which mistakes get an invoice rejected.
The law: your invoice must be serially numbered
Section 23 of the Sales Tax Act 1990 sets the rule. It says a registered person "shall issue a serially numbered tax invoice at the time of supply of goods". Serially numbered means the numbers run in order, one after another, with nothing skipped on purpose.
The Finance Act 2026 widened that same sentence. The invoice must now be one "bearing a verifiable and unique FBR invoice number". It must also be issued for exempt supplies and advance receipts, not only for ordinary taxable sales. A proviso adds that this FBR-number condition applies from the date the Board notifies.
Section 23 also carries a short line that settles a lot of arguments: "not more than one tax invoice shall be issued for a taxable supply". One sale, one invoice, one number. If you need to change a posted invoice, you raise a debit or credit note against it. You do not issue a second invoice for the same sale.
The section then lists what the invoice must show. The name, address and registration number of the supplier and of the buyer. The date of issue. The description and quantity of goods. The value excluding tax, the amount of sales tax, and the value including tax. 'FBR Digital Invoice Format: What a Sales Tax Invoice in Pakistan Must Contain (2026 Template)' covers that list field by field.
Two numbers: yours and FBR's
Your invoice number is the one your own book or software puts on the bill. Examples: INV-001, 2026-07-0042, KHI-A-1180. You control it. You must keep it in order and never repeat it.
FBR's number is different. It is the IRN (Invoice Reference Number — the unique number FBR gives every invoice once it is accepted). You cannot choose it or guess it. It comes back in FBR's reply and looks like 7000007DI1747119701593: your registration number, the letters DI, then a long time stamp.
FBR's own debit note rule describes that reference as 22 digits when it points to an NTN-based invoice and 28 digits when it points to a CNIC-based one. That length is a useful check when someone hands you a reference number and says it came from FBR.
Both numbers belong on the printed invoice. Yours identifies the bill inside your business. FBR's proves the bill exists in FBR's records. 'Invoice Reference Number (IRN) in FBR Digital Invoicing' explains the FBR side in detail.
The format FBR's system accepts
FBR checks the shape of your invoice number before it accepts the invoice. Error 0088 fires when the shape is wrong. Its wording is plain: the invoice number must be alphanumeric, with a hyphen between segments, such as Inv-001.
Alphanumeric means letters and digits only. A hyphen is allowed to separate parts. It may not sit at the start or at the end.
These pass: INV-001 · 2026-0042 · KHI-INV-1180 · 000123. A plain number with no hyphen at all is fine.
These fail: -INV001 (hyphen at the start) · INV001- (hyphen at the end) · INV/001 (a slash is not a hyphen) · INV 001 (a space) · INV#001 or INV.001 (other symbols).
Fix it once, in your billing software, rather than per invoice. Pick one pattern, put it in your settings, and every later invoice inherits it. If your invoice is being refused and you are not sure which rule broke, 'FBR Digital Invoicing Error Codes: The Complete Reference (0001–0402)' lists every code FBR can send back.
Can you restart numbering at 1 in the new year?
Yes, as long as no number ever repeats. That is the part people miss.
The safe way is to put the year inside the number. 2026-0001, 2027-0001 and so on never collide, because the year makes each one unique. Restarting at a bare 1 every July is where trouble starts: you will end up with two invoices numbered 1, and your own records stop being provable.
The same thinking covers branches. Give each branch its own letters. Then let each run its own series: KHI-0001 for Karachi, LHE-0001 for Lahore. Nothing in the law forces one single series across a whole company. But every number in your books must point to exactly one sale. 'FBR Digital Invoicing for Businesses with Multiple Branches or Outlets (2026)' covers the branch setup.
Gaps are the other question. A missing number is not illegal, but it is a question waiting to be asked in an audit. If you cancel or abandon a number, write down why. Section 23 wants numbers in order, and an officer who sees 41, 42, 45 will ask what happened to 43 and 44.
Mistakes that get an invoice rejected
Reusing a number. Your software posts the same number twice, usually after a failed attempt is retried by hand. Check whether the first attempt actually came back with an IRN before you re-post. 'FBR Invoice Failed to Post? Timeouts, No Auto-Retry, and How to Recover Safely' explains how to tell.
Repeating the same line twice inside one invoice. If two lines carry exactly the same HS Code, description, rate and unit, FBR can read the second one as a repeat and refuse it. Merge them into one line with the totals added up.
Leaving the number blank. Some spreadsheets drop leading zeros or empty the cell. An invoice with no number of your own fails section 23 before it ever reaches FBR.
Changing a number after posting. Once FBR has accepted the invoice, that pair of numbers is fixed. Corrections go through a debit or credit note, or through FBR's own 72-hour amendment window, never by editing the old number.
Keep the whole series. Section 24 of the same Act requires records to be kept for six years, and your number series is part of that record. 'FBR Digital Invoicing Record-Keeping: Six-Year Retention, Digital Signatures & Audit Readiness (2026)' sets out what to store.
Digi Invoice gives every invoice its number automatically and checks the shape before posting. It blocks a repeat. It prints your number and the FBR number together with the QR code. Create a free account and post a practice invoice before you go live. If you have not registered yet, 'How to Register for FBR Digital Invoicing (Step by Step)' is the step before this one.
Difficult words in this guide
Serially numbered: numbered in order, one after another, so that the series can be read straight through with nothing unexplained.
IRN: Invoice Reference Number — the unique number FBR returns once it accepts your invoice. You cannot choose it.
Alphanumeric: made of letters and digits only, with no spaces, slashes or other symbols.
Section 23: the part of the Sales Tax Act 1990 that says what a tax invoice must contain and that it must be serially numbered.
Debit or credit note: a separate document that adjusts an invoice already sent to FBR, used instead of changing the original.