Q: When should I say more than that I got a product for free?
A: It depends on whether you got something else from the company. Saying that you got a product for free suggests that you didn’t get anything else.
For example, if an app developer gave you their 99-cent app for free for you to review it, that information might not have much effect on the weight that readers give to your review. But if the app developer also gave you $100, knowledge of that payment would have a much greater effect on the credibility of your review. So a disclosure that simply said you got the app for free wouldn’t be good enough, but as discussed above, you don’t have to disclose exactly how much you were paid.
Similarly, if a company gave you a $50 gift card to give away to one of your readers and a second $50 gift card to keep for yourself, it wouldn’t be good enough only to say that the company gave you a gift card to give away.