Obtaining accurate electronic energies of molecules is essential for the quantitative analysis of their chemical properties. Due to its affordability and accuracy for even moderately sized systems, coupled cluster theory with single and double excitations and a quasiperturbative inclusion of connected triple excitations (CCSD(T)) is sometimes called the gold standard for quantum chemistry calculations, and is often employed for the study of thermochemistry and chemical reactions. However, although Gaussian basis sets are in principle complete so that convergence to a solution of the Schrödinger equation is guaranteed if enough Gaussians are used, the convergence of the dynamic correlation energy to the complete basis set (CBS) limit is achingly slow and can be the limiting factor in the accuracy of electronic structure calculations. This is the reason why various schemes that extrapolate the finite basis set results to the CBS limit have been developed and applied in the calculation of molecular properties. Extrapolation can greatly reduce the finite-basis-set error with no additional computational cost.