I'm here to help you accurately record your payments in QuickBooks Online (QBO), Rgby. This will ensure you effectively track your expenses.
When making a payment to your vendor for a single item, you'll need to record it as a partial payment. While you won't be able to specify which item you paid for, you can enter the exact amount paid. Here’s how to record a partial payment:
1. Click on the + New button. Then, select Pay bills.

2. From the Payment account drop-down, choose the account from which the bill was paid.
3. Set the Payment date.
4. Select the checkbox for the vendor you made a payment towards.
5. In the Payment column, type in the partial payment amount. Then, click Save and close.

If you'd like to include additional details with your payment, you can add a memo by following these steps:
1. Click on the vendor you intend to pay.
2. Select the Mark as paid at the top right corner.

3. In the Payment column, enter the amount of the partial payment.
4. Input the necessary details in the Memo section. Then, click Save and close.

Repeat these procedures each time you issue a payment to your vendor for an individual item. For further details, you can refer to this article: Enter and manage bills and bill payments in QuickBooks Online.
I also recommend generating the Bills and Applied Payments report to ensure that your recorded payments are accurately applied to the bills. You can find this under the What you owe section, located in the Standard reports tab of the Reports menu.

Additionally, using reports can also be beneficial for monitoring your cash flow and assessing your current and future financial conditions.
In case you need tips and practical solutions on how to keep your accounts balanced and free from discrepancies, our QuickBooks Live Expert Assisted can help you all the way.
Let me know if you have additional questions about handling payments to your vendor in QBO, feel free to click the Reply button below, and I'll get back to you promptly.