If you import a replica from outside of the USA it will go through US Customs. US Customs in turn will sooner or later forward a record of the import and its declared value to the state in which you reside. The state will then contact you to pay a "use tax" (sales tax) on the declared customs value. If you have your receipt for any use/sales tax paid when registering the car you can have a certified copy made of that receipt and deduct it from the amount owed the state, but that might cause some eyebrows to be raised if the declared value at registration was less (ha, ha - fraud?). The state may also impose penalties and late charges, but they'll probably be happy if you just pay the tax on the declared amount.
Your state may not have this interface with Customs or a property use tax. Mine does (Maryland), so I'm just gonna send them their blood money.
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