ENH: Following the precise nomenclature of EStG

[MImmesberger]

Is your feature request related to a problem?

I turns out we're still not 100% precise with how we name our policy functions in the ESt modules. Mainly, this is because we have many things not implemented that are part of the ESt.

Here is a very good source that get's the nomenclature right; see page 6f.

Everything up to "Gesamtbetrag der Einkünfte" is on individual level. After that, we are on sn level.

Describe the solution you would like to see

At the very least we should implement the "skeleton" of the EStG, i.e.

• Einnahmen
• Einkünfte
• Summe der Einkünfte
• Gesamtbetrag der Einkünfte
• Einkommen
• zVE
• tarifliche ESt
• festzusetzende ESt

Even if tarifliche ESt == festzusetzende ESt for now (because we're missing inputs) , this will be very helpful to keep an overview over what is missing.

[MImmesberger]

#1093 also added a quick and dirty fix to gesamtbetrag_der_einkünfte_y before 2009. This function should be on the individual level, but we cannot calculate einkünfte__aus_kapitalvermögen__betrag_y_sn on the individual level because of the Sparerpauschbetrag.

[MImmesberger]

One additional thing to look out for: What is, legally speaking, the Einkommensteuer? Is it einkommensteuer__betrag_y_sn or is it einkommensteuer__betrag_mit_kinderfreibetrag_y_sn? The Soli seems to suggest it is the latter, because according to the law, the Soli is based on the Einkommensteuer amount; but what the law refers to is our einkommensteuer__betrag_mit_kinderfreibetrag_y_sn.

Now, even if this is true, we might not want to change the labelling here as it will be confusing for users. But we should definitely document it.