Short answer. Ten days. Rule 126, Section 10 of the Rules of Court states that a search warrant shall be valid for ten days from its date; thereafter, it shall be void. A search carried out under a warrant past that period is a search under a void warrant, whatever the warrant itself says.
What the law says
A search warrant shall be valid for ten days from its date. Thereafter, it shall be void.
Rule 126, Section 10 — Validity of search warrant. Read the full provision →
Ten days, counted from the warrant's date
The period is fixed and the starting point is on the face of the document: A search warrant shall be valid for ten days from its date. The count runs from the warrant's own date — not from the day officers first attempt to serve it, and not from the day the occupant learns it exists. That makes the lifespan of any search warrant knowable from the paper itself: read the date the judge issued it, add ten days, and you have the last day on which the warrant could support a search.
Void means void
The second sentence closes every gap: Thereafter, it shall be void. Void is not voidable — the warrant does not merely become questionable after ten days, it becomes nothing, automatically and without anyone asking a court to say so. The section provides no mechanism for extending or reviving a lapsed warrant; if the authorities still want to search after the period runs out, the route the Rules leave open is applying for a new warrant, which puts the matter back before a judge.
Check the date first
If your home or business is searched, the date on the warrant is the first thing to photograph or copy. Compare it with the date of the actual search: a search conducted within the ten days stands on different footing from one conducted on the eleventh day or later, when the section says the warrant shall be void. Note the dates contemporaneously — receipts, timestamps, the inventory the officers leave — because the timeline is the sort of fact that is easy to establish immediately and hard to reconstruct months later.
One check among several
The ten-day rule is only one of the checks the Rules place around search warrants. A warrant must also be properly issued in the first place — the requirements for its issuance have their own provisions — and how the search itself is conducted is separately regulated. So expiry is one question on a longer checklist. A lawyer reviewing a search will line up the warrant's date, the date of execution, and the conduct of the search, and any one of the three can matter independently of the others.