dissolved single member LLC, confused about deadlines for the final taxt returns

Hello,

I recently dissolved my foreign-owned single member LLC. I am confused about the deadline for the Final tax returns (proforma 1120 + 5472) - should it be filed in around 4 months after dissolution (even there is not form 1120 available for 2025 yet), or the deadline to file is April 15 2026?

If the IRS will not accept my faxed tax returns, will they notify me somehow, or I need to call and ask them?

Thanks
Felix