To see which fuel credits are still available, go to IRS Instructions for Form 4136 Credit for Federal Tax Paid on Fuels. Go to IRS Publication 510 Excise Taxes (Including Fuel Tax Credits and Refunds) for definitions and information on nontaxable uses.
The IRS will not begin accepting 2025 returns that include Form 4136 until February 15, 2026. See the IRS website for details.