$$E_{\text{total}}^{\text{CBS}}={\mathcal{F}}_{\mathbf{\text{scf\_scheme}}}\left(E_{\text{total},\text{SCF}}^{\mathbf{\text{scf\_basis}}}\right)+{\mathcal{F}}_{\mathbf{\text{corl\_scheme}}}\left(E_{\text{corl},\mathbf{\text{corl\_wfn}}}^{\mathbf{\text{corl\_basis}}}\right)+{\delta }_{\mathbf{\text{delta\_wfn\_lesser}}}^{\mathbf{\text{delta\_wfn}}}+{\delta }_{\mathbf{\text{delta2\_wfn\_lesser}}}^{\mathbf{\text{delta2\_wfn}}}+{\delta }_{\mathbf{\text{delta3\_wfn\_lesser}}}^{\mathbf{\text{delta3\_wfn}}}+{\delta }_{\mathbf{\text{delta4\_wfn\_lesser}}}^{\mathbf{\text{delta4\_wfn}}}+{\delta }_{\mathbf{\text{delta5\_wfn\_lesser}}}^{\mathbf{\text{delta5\_wfn}}}$$

Here, $\mathcal{F}$ is an energy or energy extrapolation scheme, and the following also hold.

$${\delta }_{\mathbf{\text{delta\_wfn\_lesser}}}^{\mathbf{\text{delta\_wfn}}}={\mathcal{F}}_{\mathbf{\text{delta\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta\_wfn}}}^{\mathbf{\text{delta\_basis}}}\right)-{\mathcal{F}}_{\mathbf{\text{delta\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta\_wfn\_lesser}}}^{\mathbf{\text{delta\_basis}}}\right)$$

$${\delta }_{\mathbf{\text{delta2\_wfn\_lesser}}}^{\mathbf{\text{delta2\_wfn}}}={\mathcal{F}}_{\mathbf{\text{delta2\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta2\_wfn}}}^{\mathbf{\text{delta2\_basis}}}\right)-{\mathcal{F}}_{\mathbf{\text{delta2\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta2\_wfn\_lesser}}}^{\mathbf{\text{delta2\_basis}}}\right)$$

$${\delta }_{\mathbf{\text{delta3\_wfn\_lesser}}}^{\mathbf{\text{delta3\_wfn}}}={\mathcal{F}}_{\mathbf{\text{delta3\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta3\_wfn}}}^{\mathbf{\text{delta3\_basis}}}\right)-{\mathcal{F}}_{\mathbf{\text{delta3\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta3\_wfn\_lesser}}}^{\mathbf{\text{delta3\_basis}}}\right)$$

$${\delta }_{\mathbf{\text{delta4\_wfn\_lesser}}}^{\mathbf{\text{delta4\_wfn}}}={\mathcal{F}}_{\mathbf{\text{delta4\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta4\_wfn}}}^{\mathbf{\text{delta4\_basis}}}\right)-{\mathcal{F}}_{\mathbf{\text{delta4\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta4\_wfn\_lesser}}}^{\mathbf{\text{delta4\_basis}}}\right)$$

$${\delta }_{\mathbf{\text{delta5\_wfn\_lesser}}}^{\mathbf{\text{delta5\_wfn}}}={\mathcal{F}}_{\mathbf{\text{delta5\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta5\_wfn}}}^{\mathbf{\text{delta5\_basis}}}\right)-{\mathcal{F}}_{\mathbf{\text{delta5\_scheme}}}\left(E_{\text{corl},\mathbf{\text{delta5\_wfn\_lesser}}}^{\mathbf{\text{delta5\_basis}}}\right)$$

A translation of this ungainly equation to example [5] below is as follows. In words, this is a double- and triple-zeta 2-point Helgaker-extrapolated CCSD(T) coupled-cluster correlation correction appended to a triple- and quadruple-zeta 2-point Helgaker-extrapolated MP2 correlation energy appended to a SCF/aug-cc-pVQZ reference energy.

$$E_{\text{total}}^{\text{CBS}}={\mathcal{F}}_{\text{highest\_1}}\left(E_{\text{total},\text{SCF}}^{\text{aug-cc-pVQZ}}\right)+{\mathcal{F}}_{\text{corl\_xtpl\_helgaker\_2}}\left(E_{\text{corl},\text{MP2}}^{\text{aug-cc-pV[TQ]Z}}\right)+{\delta }_{\text{MP2}}^{\text{CCSD(T)}}$$

$${\delta }_{\text{MP2}}^{\text{CCSD(T)}}={\mathcal{F}}_{\text{corl\_xtpl\_helgaker\_2}}\left(E_{\text{corl},\text{CCSD(T)}}^{\text{aug-cc-pV[DT]Z}}\right)-{\mathcal{F}}_{\text{corl\_xtpl\_helgaker\_2}}\left(E_{\text{corl},\text{MP2}}^{\text{aug-cc-pV[DT]Z}}\right)$$