Build a payment list before typing
For each jurisdiction and person, list income-tax withholding, estimated installments, payments made with an extension, and a prior-year overpayment credited to the selected year. Keep supporting records beside the list. A bank debit alone may not establish the tax year or account to which an agency credited the payment.
Use the four separate fields
Enter actual estimated installments in the estimated-payments field. Enter payments for an extension of the 2025 return in the extension field. Enter a 2024 overpayment applied to 2025 in the prior-year field. Exclude transaction fees. If an old total already combines these categories, split it before entering the separate amounts so no payment is counted twice.
Zero and unknown mean different things
Enter 0 when you have verified that no payment belongs in a field. Leave an uncertain amount blank. The calculator may still show a tax liability, but it cannot determine a cash result until the required payment information is known. State-specific document, rounding and timing checks appear when they apply.
Review applied state refunds
An applied state overpayment may also require a federal taxability check. A positive state prior-year credit triggers a question about whether any of it is taxable federal income. If that issue is unresolved, this wage-only calculation stops. Payments for an amended return or an already settled original return also need reconciliation outside this release.