[ThePhysicist]

I assume if you're based outside of EU you were paid as a contractor? In that case you can start a legal dunning process (gerichtliches Mahnverfahren), that's actually surprisingly easy to start, most municipalities provide it as an online service. The court will ask you to provide some proof of the unpaid services you provided and send a court order to the company, most companies crater after that and pay. Once you have an enforcement order (Vollstreckungstitel) you can start the debt enforcement process (Zwangsvollstreckung), an official court agent will seek to retrieve the debt from the company then, going as far as seizing office assets and even cash in the founders pockets (it can be quite humiliating). As I said, it's a surprisingly easy process to get started and it's really intimidating to most companies as any legal action might lead to being publicly documented and tainting the credit score of the company, it can even lead to court ordered bankruptcy filing.

If you were actually employed you need to take the company to the labour court (Lohnklage), given how difficult it is to employ someone who's residing outside of the EU I imagine this to be even scarier for the company, so they should be very willing to settle their debt with you.

Again, the key point is to plausibly threaten and possibly enact these measures. This is not legal advice.

[qazwsxedchac]

Note that if you are based outside Germany and you want to start a "Mahnverfahren" then you'll need to start it at the district court of Berlin-Wedding

https://www.mahngerichte.de/mahngerichte/wedding/

not at any other municipality's court.

Only do this yourself if you speak and read German well enough to handle the correspondence yourself. Otherwise you really need a German lawyer to act for you.

It is sometimes possible to agree payment of lawyer's fees according to the value in dispute instead of being billed for time spent. This can keep costs down.

[kiraken]

Yes, I was hired as a contractor. The company is based in Köhlstraße, do you know which municipality website I need to file the complaint from?

[mtmail]

You didn't mention the city name. There's several Kohlstraße in Germany but only one Köhlstraße it seems, that would be in Cologne (Köln). Suburb is Ossendorf, District (Bezirk) is Ehrenfeld and if any form asks for a Bezirksnumber, it's 4.

Cologne has only one district court (Amtsgericht), that's https://www.ag-koeln.nrw.de/

Of the various Zwangsvollstrecking I think the Forderungsvollstreckung (you want to force somebody to pay their bill) is the relevant one https://www.justiz.nrw/BS/lebenslagen/zivilrecht/Zwangsvolls...

I'm not familiar in this legal area. You'll need at least somebody to translate the documents. I know one (well, a German resident) can do everything themselves for very low cost, I think 30 Euro. That's what contractors in Germany do when their bills are not paid.

Basically you tell the local court your demand, the court will notify the company and if they don't pay then the court will find ways to get the money. All the way to literally send somebody to their office and take their printer, office chair or company car and sell it. That part of justice is sweet (and funny) but usually it's letters send back and forth.