In most state and federal facilities, inmates have access to a system that lets them check their account balances without needing someone on the outside to tell them. At the federal level, the Trust Fund system allows inmates to check their account through the TRULINCS terminals available in many units. State systems typically have a similar kiosk or terminal setup where inmates can view their trust account balance, which includes phone funds depending on how the facility structures its accounts.
That means your nephew can check on his own whether funds have arrived without waiting for a call or a letter from you. Most inmates check their balances regularly, particularly when they are expecting money to come in.
That said, letting him know you have set up the account is still worth doing, especially if he does not know to look for it. A letter through InmateAid is the most reliable way to get that information to him if you have not spoken recently. Include the details he needs, specifically which account the funds are on and how to access them, so he is not guessing.
One thing worth confirming is whether the money you added went to the right account. Phone funds and general commissary or trust funds are separate in many systems, and money deposited to one does not automatically transfer to the other. If you added funds through the facility's phone carrier directly, those funds are available for calls. If you deposited to his general trust account, he may need to transfer funds to the phone system depending on how that facility handles it.
A quick call to the facility's business office can confirm the funds landed in the right place.