  We review the status of the Standard Model theory of neutron beta decay.
Particular emphasis is put on the recent developments in the electroweak
radiative corrections. Given that some existing approaches give slightly
different results, we thoroughly review the origin of discrepancies, and
provide our recommended value for the radiative correction to the neutron and
nuclear decay rates. The use of dispersion relation, lattice Quantum
Chromodynamics and effective field theory framework allows for high-precision
theory calculations at the level of $10^{-4}$, turning neutron beta decay into
a powerful tool to search for new physics, complementary to high-energy
collider experiments. We offer an outlook to the future improvements.
