The maker owns it, unless it was transferred to you in writing. That holds even for work you paid for in full, and in an agency switch it is the most expensive surprise there is.
The rule
In Belgium copyright stays with whoever made the work. Paying for the assignment is not the same as buying the rights: those only pass with a written transfer stating what passes, for what use, for what territory and for how long.
If your contract says nothing, you usually hold a right of use for what the work was made for, and nothing beyond it. You discover that when you want to reuse that campaign on a new channel, or when another agency wants to build on it.
What it is about in practice
- The source files. A pdf is not a design. Without the working files your successor cannot adapt anything and has to remake it all.
- Photography, music and fonts. Almost always licensed for a period, a territory and a use. Those licences are rarely in the advertiser's name, and they expire.
- Models and voices. Contracts with a term, where an extension is a fresh negotiation.
- Code and templates. A website running on an agency's own framework is technically not simply portable.
- Data and accounts. Analytics, ad accounts, domain names. Make sure those are in your name and not the agency's. This is the item forgotten most often and the one that hurts fastest.
What to settle today
Put in the contract, in one paragraph: which rights transfer on payment, what happens to source files at the end of the relationship, and which licences are in your name. At the start that paragraph costs nothing. At the end it costs weeks and sometimes work that has to be remade.
And if the contract says nothing about it
Simply ask, before the termination letter. An agency leaving on good terms usually hands over the source files, even without an obligation. Ask after a difficult parting and it becomes a negotiation in which you hold the weakest position.
This is a general explanation and not legal advice; have your contract reviewed by someone qualified. At IKAg this clause is on the list by default when we put an agency contract next to the scope and the remuneration: see Agency evaluation & remuneration.
See also: what to put in an agency contract and how to make sure the handover goes well.