Stack was co-founded by Paul Withers, who is also the owner of Direct Bullion, for which Farage is a brand ambassador.
The gold trading company has paid him £226,200 for promotional work, according to the MPs register of interests.
Labour Party chair Anna Turley said: “Nigel Farage is hyping up a former Tory chancellor who crashed the economy, in a bid to line his own pockets.
“Reform are more interested in themselves than in standing up for working people.
“While Labour is working to clear up the mess the Tories left, Nigel Farage is cosying up to the architect of Liz Truss’s catastrophic mini-budget.
“It tells you everything you need to know about whose side he’s on.”
Keir Starmer has said he will ban donations in cryptocurrency to UK political parties in response to a review of foreign financial interference.
The crypto assets recommendation is particularly relevant to Reform UK, which is currently the only party at Westminster known to have received donations in the digital currency.
Last May, Reform UK leader Nigel Farage announced his party would accept donations in Bitcoin.
In October last year, Farage said the party had already received a “couple” of crypto donations.
Reform UK’s website says it does not accept anonymous donations and any donations above £500 are subject to checks.
In the UK, parties must check donations over £500 are from permissible sources, which include people listed on the UK electoral register.
A spokesman for Farage told the BBC that “all parties need donations to run campaigns” and “Labour taking money from the trade unions is just one example”.