adjustment for customer payment

@SHF1 

There are a number of ways to do it but in this case I think a journal entry (JE) is best.  Create a JE that debits A/R and credits your bank account $30.  That creates a $30 balance due from the customer and reduces your bank balance by $30 so it can be reconciled against your statement.   

Thanks for reaching out to us regarding your concern, @SHF1. Let me help you adjust your payments in QuickBooks Online (QBO).

There are ways to correct the balance adjustment. You can delete the original deposit to update your records or create a JE. Nonetheless, I agree with @Rainflurry's suggestion. Since you don't want to alter the original deposit amount, creating a journal entry is the best option to adjust the customer balance.

I recommend consulting with your accountant for guidance on the appropriate debit and credit entries and the affected accounts to ensure accurate tracking. If you don't have one, you can find a professional through this link: Find an accountant

On the other hand, If you'd like to delete the original deposit and match it with the transaction given by your bank, Here's how you can do it:

1. Go to the Transactions menu and select Bank Transaction.
2. First, locate and tap the $300 transaction provided by your bank, and click the Match button.

     3. Find the original invoice amount and tick the box to select it.

     4. Then, click Match.

     5. After, locate and tap the remaining $30 amount, then match it with the showing $30 open balance amount of the same invoice you selected.

     6. Click the Match button.

Additionally, refer to this article for further assistance in obtaining an accurate book: Reconcile an account in QuickBooks Online.

Keep us posted if you have other questions about managing payments. I'll be around to help. Take care.

@MichaelaS 

"If you've already recorded a deposit in QBO, you should delete the original deposit to correct your records to maintain accurate tracking."

Really?  I think you missed this part from your customer:

"how do I adjust the customer balance to reflect the actual payment made without altering the original deposit amount?"

Does anyone from QB even read their customer's issues?  

@MichaelaS 

If you edit your post after being quoted, it makes me look like I'm quoting something you didn't post but did.  You should reference any edits you make or create a new post.