Mantle crypto tax UK 2025/26

How HMRC taxes Mantle disposals

For UK tax purposes, HMRC treats Mantle the same way it treats any other cryptoasset. Every swap, sale, gift, or use of MNT to buy goods is a disposal under TCGA 1992 — even if you didn't touch GBP.

The matching rules apply in this order:

1. Same-day rule (s.105 TCGA) — disposals are matched first against any acquisitions on the same calendar day, irrespective of price.
2. 30-day bed-and-breakfast rule (s.106A) — any remaining disposals are matched against acquisitions in the next 30 days. Designed to stop sell-then- rebuy gaming of the cost basis.
3. Section 104 pool — everything left enters a single pooled position valued at average cost. Your gain on each remaining disposal is proceeds minus the pool's average cost basis at that point in time.

The first £3,000 of net gains in 2025/26 is covered by the annual exempt amount. Above that, you pay 18% in the basic rate band and 24% in the higher band, applied per disposal date (the rate split changed on 30 October 2024 — disposals before that date use the old 10/20% rates; CryptoLens applies the right rate per disposal automatically).

What counts as a disposal on Mantle

• Selling MNT for GBP (or any fiat)
• Swapping MNT for any other token, including stablecoins
• Bridging MNT to a different chain (some bridges are no-gain-no-loss; CryptoLens flags known migrations under HMRC CRYPTO22110 and excludes them from the CGT pool)
• Using MNT to buy NFTs, mint, or pay gas on a different chain
• Gifting MNT to anyone other than a spouse or civil partner

Income vs capital — what to flag separately

Some Mantle activity is income, not capital — taxed via Self Assessment SA100 / SA107 not the SA108 schedule:

• Staking rewards — FMV at receipt is miscellaneous income (HMRC CRYPTO21200)
• Airdrops you didn't earn — FMV at receipt is income; cost basis for future CGT = the FMV
• Mining (if Mantle supports it) — same FMV-at-receipt treatment
• Liquidity provision rewards — generally income; the LP-token mechanics depend on protocol type and are surfaced under CryptoLens's DeFi treatment toggle

What CryptoLens does for Mantle

• Reads every disposal on-chain. Paste a wallet, we walk every MNT swap, transfer-out, and protocol interaction in the address's history.
• Prices each disposal at the moment it happened. Hourly historical MNT/GBP from CoinGecko + per-second Birdeye for Solana spot, with DefiLlama and GeckoTerminal as fallbacks for older or rugged tokens.
• Runs the HMRC engine. Same-day → 30-day → Section 104, in order, with multi-year carry-forward losses (CG14580) and the annual exempt amount applied per disposal date.
• Hands you an SA108 PDF. Line-by-line proceeds, cost basis, gain/loss, with the matching method noted for each disposal — drops straight into a Self Assessment return. Audit trail included for HMRC enquiries.

Where your Mantle data comes from

We read directly from the Mantle blockchain via the public network — no third-party tax-tool reseller in the chain of custody. Historical prices come from CoinGecko's public API (mantle) with secondary fallbacks. Every disposal in your SA108 PDF is traceable back to a transaction hash and the price-source label (CoinGecko, DefiLlama, GeckoTerminal, Birdeye, native-flow).