First of all, if you are an employee AND you do not have any stocks/other incomes it is not mandatory for you to do a taxes declaration. However, it is reccommended to do it, especially the 1st year since you will get quite some money back to cover the expenses of your moving.
If you decide to do the declaration, check carefully the deadline for the documents presentation on the website of your tax office (Finanzamt). After the deadline it will still be possible to present your documents, but you might have to pay a fee.
You have 4 years to declare your incomes. For example, you arrived in Germany on the 2018, so you have time until the 2022 to present the taxes declaration for the 2018.
Then there are 2 main cases, related to how many months you have been working in Germany the year you want to do the declaration of:
- You were working in your home country for some months and then you moved to Germany and started working there (for example, you worked from January to September in your home country and from October to December in Germany)
- You worked in Germany from January until December
1st case: you need to check with your home country which is the regulation in these cases (it varies from country to country and it depends on agreements between countries). Normally what is done is: you pay taxes in the country in which you habe been working most of the time (number of days greater than a certain threshold).
So, following the example above: you worked 9 months in your home country and 3 months in Germany, therefore you first declare your incomes in your home country. Your home tax office will have to fill in a document called Bescheinigung EU/EWR (you have to download it from the Finanzamt website and bring it to your home tax office). When you do the taxis declaration in Germany you have to present the Bescheinigung EU/EWR.
So you will have to do a taxes declaration in each country, but the Bescheinigung EU/EWR prevents the double taxation.
If you fall in this case, I suggest to rely on a tax consultant (Steuerberater). It will cost you a bit, depending also on your income (roughly should be around 250€), but you save yourself a lot of problems. A good rule anyway is: before letting the consultant doing the job for you, ask an estimate of the costs, if it is far more than 250/300 € I would look for another one.
2nd case: this is the easy one, you just need the income tax certificate (Lohnsteuerbescheinigung) from your company/employer and then it is only a matter of filling in the numbers in the tax declaration module.
Although it is simple, since it is your first time I suggest to rely on one of the available help-softwares you can buy online (from Amazon or from the website of the Finanzamt).
These softwares offer a guided procedure to fill in your module and they also provide videos to explain the topic. The costs is affordable (it varies roughly from 15€ to 30€), but you need a bit of knowledge of German to use them (or Google translate :) ), because there is no other language available.
Once you have filled in the module, you just have to sign it and bring it to your tax office (Finanzamt).
Other common things you can put into your taxes declaration:
- liability insurance (Haftpflichtversicherung), if you have one
- accident insurance (Unfallversicherung), if you have one
- Kilometers from your house to your working place and number of working days (they pay back 0.30€ per km)
For any question you can always ask directly to the Finanzamt, however keep in mind that they will NOT fill in the module for you.