How should I enter an additional payer payment?

Count it once. Enter the original payer payment in the main payment field and any separate additional payment in the optional field. If your main total already includes the additional payment, leave that optional field at zero.

The same payment, two valid ways

In a worked example, the expected payer share is $5,470. The initial payment is $4,730 and a later payment adds $600. Total payer payments are $5,330, leaving a $140 difference.

You can enter $4,730 plus $600, or $5,330 plus zero. Both should give $140. Entering $5,330 plus another $600 counts the later payment twice and produces a misleading result.

What if the result is negative?

Check for a duplicate payment in your inputs first. Then check whether the expectation and payment total refer to the same population. A negative result alone does not establish an overpayment.

Reversals and offsets need a separate check

A reversal, offset, or provider-level adjustment may need separate review. The tool does not match an ERA to a deposit or assign an adjustment to a particular case. CMS’s remittance guidance explains those distinctions in the Medicare setting.

Try the payment calculator with the totals above. Keep remittance and payment identifiers in your organization’s systems.