Before you start

Steuer-ID, issued automatically after Anmeldung
Understanding of your tax class, if you are on an ordinary German contract
Written confirmation of your tax position, if you are on an international-organisation contract
Records of foreign income and foreign accounts
An ELSTER account, if filing yourself

Step-by-step

1
Establish your regime before your first payslip
If your employer is an international organisation, your salary may be taxed under a separate arrangement rather than through German payroll, and your social insurance and pension may sit outside the German system too. Get it in writing from HR, and take professional advice on how any other income you have interacts with it.
Via employerWho: Your organisation's HRBefore your first payslip
2
Give your employer your Steuer-ID as soon as it arrives
For ordinary German contracts: until they have it, payroll applies the least favourable class and a large amount comes off your pay — recoverable at filing but painful in your first months.
Via employerWho: YouAs soon as issued
3
Understand your tax class
Steuerklasse determines monthly withholding: class 1 for single people, 3/5 or 4/4 combinations for married couples. Choosing 3/5 where incomes are uneven reduces monthly withholding, though the annual liability settles at filing either way.
OnlineWho: You
4
Check your church tax position
If you declared church membership at Anmeldung, 9% of your income tax is deducted automatically in NRW. Leaving formally requires an appointment and a fee, and takes effect from the following month rather than retrospectively.
In personWho: You
5
Claim the commuting allowance if you travel to Cologne
The Entfernungspauschale is a per-kilometre deduction for the distance between home and workplace, claimable however you travel — so it applies even though the Deutschlandticket already covers the Stadtbahn. Commuting between Bonn and Cologne is entirely normal and generates a substantial annual deduction.
OnlineWho: You
6
File a return even if not required
A return frequently refunds — commuting costs, work equipment, relocation expenses, professional training and double-household costs are all deductible. The relocation year especially.
OnlineWho: YouBy 31 July following the tax year

Documents you’ll need

Steuer-ID
Lohnsteuerbescheinigung — the annual employer certificate, for ordinary German contracts
Written confirmation of your tax regime, for international-organisation contracts
Records of deductible expenses, including the move and the commute
Foreign income and account records

Things most newcomers don’t know

A household with one institutional salary and one German salary needs an adviser, not a forum.

Bonn produces this combination constantly: one partner on an international-organisation contract outside the ordinary German payroll regime, the other on a normal German one. How the two interact for tax class, the household's overall rate, allowances and pension credit is genuinely complicated and gets answered wrongly on expat forums with great confidence. A single session with a Steuerberater in your first year pays for itself.

Source: community-reported

Church tax is 9% in NRW and you opt in at registration.

Declaring church membership during the Anmeldung triggers automatic deduction of 9% of your income tax. It is decided in a short appointment most newcomers do not realise has a price, and leaving later requires a formal appointment and fee.

Source: Finanzverwaltung Nordrhein-Westfalen

Pension credit is the thing people forget to ask about.

Years worked on an ordinary German contract build entitlement in the statutory pension system. Years on an institutional contract may build entitlement in that organisation's own scheme instead, and the two do not automatically add up. If you expect to spend a career partly in each, ask early how the periods are treated — it is far easier to plan for than to fix.

Source: Deutsche Rentenversicherung

Relocation costs are deductible and the moving-year return usually refunds.

Costs of a work-related move — transport, travel to view flats, double rent during the transition, and a flat-rate incidentals allowance — are deductible for those inside the German system. New arrivals frequently do not file in their first year and leave a refund unclaimed.

Source: Bundesministerium der Finanzen

Common mistakes to avoid

Assuming an international-organisation salary is taxed like a German one, or vice versa.
Taking tax advice for a mixed-regime household from an expat forum.
Declaring church membership at Anmeldung without realising it triggers 9% church tax.
Not claiming the commuting allowance when you travel to Cologne daily.
Not filing a return in the relocation year and forfeiting a likely refund.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.