The short answer
Under Section 5 of the Bangladesh Patent Act, 2023 the priority date is the earliest date you can rely on. A provisional filing fixes it. A foreign filing can fix it if you file in Bangladesh within 12 months. A divisional keeps the parent's date.
How the priority date is set
| Situation | Priority date |
|---|---|
| Provisional filed first | Filing date of the provisional |
| Foreign filing first (Paris Convention) | Foreign filing date, if you file in Bangladesh within 12 months for the same subject matter, with documents |
| Divisional application | Same as the parent, if disclosed there |
| Several earlier applications | Each claim gets its own matching date |
| Certified copy of the earlier application | The Director General can require it within the time set by the rules (Section 5) |
Why the date decides the outcome
The priority date fixes novelty and who filed first. Anything published or filed by others after that date cannot be used against you.
Example. Provisional filed 1 January 2025, complete specification 1 June 2025: your priority date stays 1 January 2025. A rival filing a similar invention on 10 March 2025 loses to you.
Documents and formalities
The government may set how priority documents are filed, including forms, languages and deadlines, and may allow electronic filing. Check the current rules with your agent before filing.
Priority date questions
How long do I have to claim foreign priority?
12 months from the first foreign filing date.
Does a provisional set the priority date?
Yes. The provisional filing date is the priority date for the later complete specification.
Is a certified copy of the foreign application needed?
Yes. The Director General can require a certified copy from the office where the earlier application was filed, within the time set by the rules (Section 5).
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