or performed the taxable services invoiced, and (4) not been paid 180 days after date the invoice was due to be paid, shall be entitled to a credit equal to the amount of tax remitted and unpaid by the purchaser. (c) Subsequent Payment Any payment made with respect to a transaction subsequent to a section 205 credit being taken with respect to that transaction shall be subject to tax in the month the payment was received as if a tax inclusive sale of taxable property and services in the amount of the payment had been made. (d) Partial Payments Partial payments shall be treated as pro rata payments of the underlying obligation and shall be allocated proportionately— (1) for fully taxable payments, between payment for the taxable property and service and tax, and (2) for partially taxable payments, among payment for the taxable property and service, tax and other payment. (e) Related Parties The credit provided by this section shall not be available with respect to sales made to related parties. For purposes of this section, related party means affiliated firms and family members (as defined in section 302(b)). 206. Insurance proceeds credit (a) In General A person receiving a payment from an insurer by virtue of an insurance contract shall be entitled to a credit in an amount determined by subsection (b), less any amount paid to the insured by the insurer pursuant to subsection (c), if the entire premium (except that portion allocable to the investment account of the underlying policy) for the insurance contract giving rise to the insurer’s obligation to make a payment to the insured was subject to the tax imposed by section 101 and said tax was paid. (b) Credit Amount The amount of the credit shall be the product of— (1) the rate imposed by section 101, and (2) the quotient that is— (A) the amount of the payment made by the insurer to the insured, divided by (B) the quantity that is one minus the rate imposed by section 101. (c) Administrative Option The credit determined in accordance with subsection (b) shall