Before you start

Tax residency in Germany (your main or habitual home is here)
Your tax ID (Steuer-Identifikationsnummer) — posted automatically after your Anmeldung
An employment contract so payroll can run Lohnsteuer withholding
A German bank account for salary and any tax refund

Step-by-step

1
Give your employer your Steuer-ID and tax class
Hand your 11-digit Steuer-Identifikationsnummer to payroll. Your tax class (Steuerklasse) — Class I if single, III/V or IV/IV for married couples, II for single parents, VI for a second job — sets how much Lohnsteuer is withheld each month. It affects monthly take-home, not your final tax bill.
Via employerWho: You + employerBefore your first payroll runFree
2
Let Lohnsteuer be withheld automatically
Each month your employer deducts wage tax (Lohnsteuer), plus the solidarity surcharge if you are a high earner and church tax (Kirchensteuer, 8–9% of your income tax) if you registered as a member of a recognised religion. You receive the net amount; nothing else is required from you during the year.
Via employerWho: EmployerEvery payslipWithheld from gross pay
3
Decide whether you must file or want to file
Filing is mandatory in some cases (multiple jobs, sizeable side income, class III/V couples, certain benefits). Even when optional, most single employees file voluntarily because deductions — commute, moving for work, home office, insurance — typically produce a refund. You generally have up to four years to file a voluntary return.
OnlineWho: YouFrom January after the tax yearFree (or ~€30–40 for tax software)
4
File the Steuererklärung via ELSTER or tax software
Submit your return through the tax office's free ELSTER portal or an English-friendly tool (WISO, Taxfix, SteuerGo). The Finanzamt assesses it and pays any refund to your bank account. The mandatory deadline is 31 July of the following year; voluntary filers have far longer.
OnlineWho: YouRefund typically in weeks to a few monthsELSTER free; software ~€30–40

Documents you’ll need

Tax ID (Steuer-Identifikationsnummer)
Annual payslip summary (Lohnsteuerbescheinigung) from your employer
Records of deductible costs (commute, home office, moving, insurance, donations)
German bank details (IBAN) for the refund
ELSTER account or tax-software login

Things most newcomers don’t know

Your Steuerklasse sets monthly take-home, not your real tax bill.

The tax class only decides how much Lohnsteuer is withheld each month; your true liability is computed when you file. A class that over-withholds simply means a bigger refund later, so an unexpected class is rarely a disaster — it is reconciled at year-end.

Source: Make-it-in-Germany (salary, taxes & social security)

Filing a voluntary Steuererklärung usually gets money back.

Even when you are not obliged to file, deductions for commuting, moving for a job, home-office costs and insurance often mean the Finanzamt over-withheld during the year. Most single employees who file voluntarily receive a refund, and you have up to four years to claim it.

Source: Make-it-in-Germany / Bundeszentralamt für Steuern

The headline 45% is a marginal rate — you never pay it on your whole income.

Germany taxes progressively under § 32a EStG: the first ~€12,348 is tax-free, then each band is taxed at a rising rate from 14% to 42%, and only income above roughly €277,826 touches 45%. Your average rate is far below the top bracket you reach.

Source: § 32a EStG (gesetze-im-internet.de)

Church tax is only charged if you register as a member — and it is 8–9% of your income tax.

If you state a recognised religion at your Anmeldung, Kirchensteuer (8% in Bavaria and Baden-Württemberg, 9% elsewhere including Berlin) is added on top of your income tax and withheld via payroll. Declaring no religious affiliation avoids it; you can also formally leave the church (Kirchenaustritt) later.

Source: Make-it-in-Germany / PwC tax summaries

Common mistakes to avoid

Reading your Steuerklasse as your tax rate — it only sets monthly withholding, reconciled when you file
Skipping a voluntary return and leaving an over-withheld refund unclaimed
Not realising church tax was triggered by the religion field on your Anmeldung
Missing the 31 July deadline when you are in the mandatory-filing group (e.g. class III/V couples or side income)
Forgetting that as a tax resident your worldwide income, not just German salary, is in scope