When you sign a publishing deal, you'll either assign or license your copyrights to the publisher. The specific arrangement depends on your contract. In a traditional deal, you might assign your copyrights to the publisher for the term of the agreement, though you'll always retain your writer's share (50%) of performance income collected by PRS.
An admin deal typically involves licensing rather than assignment (you retain ownership while the publisher handles registration and collection). In co-publishing deals, you might assign copyright but retain a share of the publisher's income. The key is understanding what rights you're granting and for how long. Most deals include reversion clauses, meaning your copyrights return to you after a set period or when certain conditions are met. Always seek legal advice before signing, as these agreements fundamentally affect your rights and income.