The unitary nature, so convenient for paying official fees, has a downside: any change affecting the patent affects it everywhere simultaneously. Limitation, revocation, lapse: nothing is done à la carte.
The principle: effective against all
A unitary patent can only be limited, revoked, or lapse with respect to all participating member states (Article 3(2) of Regulation 1257/2012). This is the price of unity.
Centralized limitation and revocation before the EPO
The proprietor may, on their own initiative, request limitation or revocation of their patent centrally before the EPO (limitation and revocation procedure under Articles 105a to 105d of the EPC): the effect is then uniform across the entire unitary territory.
Revocation by the UPC
Moreover, a third party may obtain the revocation of the unitary patent before the Unified Patent Court (Article 65 of the Agreement on a Unified Patent Court), whether through a direct action for invalidity or a counterclaim in an infringement action. A single decision, and the patent falls everywhere.
This is the double-edged sword of the system: a single proceeding is sufficient to enforce the patent across eighteen states… but a single proceeding is also enough to invalidate it across all eighteen. This risk of central revocation is precisely what drives some proprietors of classic European patents to opt out of the Unified Patent Court (see The transitional regime: opt-out and opt-in)—an option that, however, is not available for the unitary patent, which is inseparable from the UPC.
Lapse
Finally, the patent lapses in the event of non-payment of annual official fees: once again, this applies to the entire territory at once (see Lapse and restoration of rights).