I would like to return this item.
Stress 'REsti-TUI-re' — four syllables, accent on the second.
Use this as your opening line when approaching the counter to return something. It is polite and direct without being demanding. Works in any shop from a supermarket to a boutique.
The conditional 'vorrei' (I would like) softens the request and is considered more polite than the present tense 'voglio' (I want). 'Restituire' means to give back or return an item. Italians expect a calm, formal tone when making returns.
Vorrei rendere questo articolo.
I would like to return this item.
Rendere is equally common in northern Italy.
Devo restituire questo.
I need to return this.
Slightly more urgent tone.
Posso restituire questo acquisto?
Can I return this purchase?
Asking permission — very polite.
Italian shops are not legally required to accept returns unless the item is defective. Many have a 'cambio merce' (exchange only) policy. Always check before buying.