Focus on UK Metal Detecting: Paying Tax

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The Land Gazette, a daily updated news website for British landowners and land professionals two years ago carried a brief (though muddled) text on the tax status of Treasure rewards in the UK (John Vaughan, 'Treasure Trove: Landowners can claim tax-free rewards', Thursday, 16 September 2010):

The discovery by a metal detector enthusiast of a rare bronze Roman helmet and mask, in a field near the village of Crosby Garrett in Cumbria, with an estimated value of £300,000, will have landowners and farmers thinking about what might lie under their land.  Commenting on the implications of such a valuable find, Andrew Arnott of Saffery Champness says:: “If an item or items are declared treasure trove under the wording of the Treasure Act 1996 and the finder receives a cash reward from the Crown there are no tax consequences. It is a pure gift of cash and is not chargeable either to Income Tax or Capital Gains Tax. “However, as is the case with the find of the Roman helmet and mask, items that are not deemed to be treasure trove and where the finder sells them, usually having reached a share agreement with the landowner, are treated as chattels. If the sale proceeds of an individual item exceed £6,000 then Capital Gains Tax would be applicable”.

The use of the term Treasure Trove for an English find is of course an anachronism, as is setting out TT 'law' in the following part of the text. So basically selling artefacts from a rally or detecting permission on eBay or to a dealer may in certain situations be taxable.
Richard Evans ('Gold: what to do if you dig up your own Anglo-Saxon hoard', Daily Telegraph Investments section 02 Oct 2009 - Will I have to pay tax on valuable finds?) explains:

If you sell a valuable find, you will be liable to pay capital gains tax (CGT) on any amount above the annual exemption of £10,100 per person. Stephen Herring, a tax partner at BDO Stoy Hayward, the accountancy firm, said: "It would be very unlikely that HM Revenue & Customs would view a casual discovery as a 'trade', so it would not apply an income tax treatment. They would probably anticipate that more people would make a loss in any case. Accordingly, a disposal would be treated as a capital gain. Above the £10,100 annual exemption a fixed rate of 18pc is payable." An additional "chattels exemption" would probably apply, he added. "This applies, on an item-by-item basis, where the proceeds of the sale of tangible movable property, excluding currency of any description, are under £6,000." British gold sovereigns, which are still legal tender, are exempt from capital gains tax, Mr Herring added.

In the US (Carter McBride,'Reporting Earnings From Metal Detecting to the IRS') income from metal detecting apparently is taxable:

All earnings, including valuables you find with your metal detector, must be reported to the Internal Revenue Service (IRS). The IRS will tax the gain from the findings, in much the same way prize winnings are taxed. If a person wins a prize, he must report the fair value of the prize as income. The IRS then taxes the income as if the person earned the money as wages during the year.