Three to six months is common in the Belgian market. That is practice, not law: there is no statutory notice period for a services agreement between businesses, so whatever your contract says applies.
What the length should follow from
How many people the agency dedicates to you. An agency with three people full time on your account cannot redeploy them in a month; an agency serving you two days a month can. Six months is therefore reasonable on a large retainer and excessive on a small contract.
A second consideration is the time you need to find a successor. A selection takes two to four months, plus handover on top. A one-month notice period means you will be left without an agency.
The rule never to drop
Reciprocity. The same period for both parties. A contract where you must give six months and the agency one is not an agreement, it is a penalty. Check it explicitly: it is one of the most common imbalances in standard contracts, usually with no bad intent.
What to settle alongside it
- What still happens during the notice period. An agency that knows it is leaving puts its best people elsewhere. Write down which team stays on your account.
- What happens to running projects. Finish, hand over, or stop with a settlement.
- When handover starts. Preferably at notice rather than in the final week. See how to make sure the handover goes well.
- An exit for non-performance, with a definition of what that is. Without that clause you are tied to a relationship that does not work.
The practical tip
Say it in person before the letter goes out, even when you are contractually not obliged to. It costs you nothing and changes everything about how the final months run. See how to end things with an agency properly.
A notice period that is not reciprocal is one of the things IKAg straightens out when we put a contract next to the scope and the remuneration. See Agency evaluation & remuneration.
See also: how long an agency contract should run and what to put in a contract.