Deductions are a key factor in determining taxable income in Canton Basel-Stadt. Starting from gross income, a range of deductions can significantly reduce the amount subject to federal, cantonal and communal income tax.

This page provides an overview of the main deduction categories under Basel-Stadt income tax law and how they interact with federal rules. Exact amounts, lump-sums and caps depend on the tax year and the legislation in force.

Principles of Deductions in Basel-Stadt

Basel-Stadt broadly follows the general Swiss approach to deductions. In practice, the system recognises:

• Employment-related and professional expenses,
• Mandatory social security and occupational pension contributions,
• Tax-privileged private pension savings (Pillar 3a),
• Insurance premium and interest-related deductions within set limits,
• Family-related deductions and social allowances,
• Property-related deductions for homeowners and landlords,
• Extraordinary and unavoidable expenses (e.g. high medical costs).

While many categories mirror federal rules, Basel-Stadt applies its own lump-sums, ceilings and administrative practice.

Employment-Related Deductions

Employees in Basel-Stadt can deduct expenses directly connected with earning their employment income. Typical categories are:

• Professional expenses – usually claimed as a lump-sum based on a percentage of salary, or as documented actual costs if higher and accepted by the tax authorities.
• Commuting expenses – travel between home and the regular workplace, generally based on public transport costs; deductions for private car use are subject to restrictive conditions and cantonal caps.
• Other job-related costs – such as mandatory professional memberships, certain licences or job-specific tools.

Whether a taxpayer can switch from lump-sum to actual expenses depends on cantonal practice and sufficient documentation.

Social Security and Occupational Pension Contributions

Contributions to mandatory social security and occupational pension schemes are generally fully deductible. This includes:

• AHV/IV/EO contributions,
• ALV (unemployment insurance),
• Mandatory occupational pension contributions (2nd pillar),
• Recognised voluntary 2nd-pillar buy-ins within statutory limits.

These amounts are usually deducted at source and documented in the Swiss salary certificate, which forms the basis for the tax return.

Private Pension Savings (Pillar 3a)

Contributions to tax-privileged private pension schemes (Pillar 3a) are deductible up to the federal annual maximum. Basel-Stadt follows the federal framework without major cantonal deviations.

• Taxpayers with 2nd pillar coverage have a standard annual limit,
• Taxpayers without 2nd pillar coverage (e.g. self-employed) benefit from a higher Pillar 3a limit.

Insurance Premiums and Interest on Savings

Basel-Stadt grants deductions for certain insurance premiums and, in some cases, interest on savings and similar income, within combined federal and cantonal rules. Typically:

• Health insurance and qualifying life insurance premiums,
• Interest on savings within the framework of the insurance/interest deduction,
• Overall caps that depend on marital status and the presence of dependent children.

The exact allowance is determined by cantonal limits for each tax year.

Family-Related Deductions and Allowances

Taxpayers with dependants benefit from a range of family-related deductions, for example:

• Child deductions for each dependent child,
• Deductions for dependants in need of support (e.g. elderly parents),
• Special deductions or social allowances for single parents.

The deduction amounts are set in Basel-Stadt tax legislation and may differ from federal amounts and those of other cantons.

Second-Earner Situations

At federal level, households where both spouses or registered partners are working benefit from a second-earner deduction. Basel-Stadt reflects these federal rules and applies its own cantonal rate structure to the resulting taxable income. In practice, this reduces the tax burden on dual-income households compared to taxation without such relief.

Childcare Costs

Childcare costs may be deductible when they are necessary to enable:

• Gainful employment by one or both parents, or
• Education or training of the parents.

Typical conditions include:

• Documented expenses (invoices, contracts),
• Recognised forms of childcare (e.g. nurseries, daycare centres, after-school care),
• Cantonal maximum amounts per child and per year.

Education and Training Costs

Basel-Stadt generally allows deductions for continuing education and training that is closely linked to the taxpayer’s current profession or professional development. Examples include:

• Professional development and continuing education courses,
• Postgraduate programmes related to the existing occupation,
• Specialised seminars and courses that enhance professional skills.

Initial education for a first profession is typically not deductible, in line with federal practice.

Property-Related Deductions

Property owners in Basel-Stadt must declare rental income or imputed rental value, but they may benefit from property-related deductions, such as:

• Mortgage interest on loans secured by the property,
• Maintenance and repair costs, either actual expenses or a lump-sum based on cantonal rules,
• Recognised renovation expenses that preserve, but do not enhance, the value of the property.

Value-enhancing investments are generally not immediately deductible and are treated as capital improvements.

Extraordinary Expenses and Medical Costs

Certain extraordinary expenses may be deducted if they are unavoidable and exceed a defined proportion of income. Typical examples include:

• High medical and dental costs not reimbursed by insurance,
• Disability-related expenses and necessary assistance,
• Support payments to persons in financial distress that exceed normal living expenses.

The thresholds and qualifying criteria are laid down in cantonal law and administrative practice; detailed documentation is essential.

Cross-Border Situations and Allocation Rules

For taxpayers with income or assets outside Basel-Stadt or abroad, deductions and relief mechanisms may arise in the context of:

• Double Taxation Agreements (DTAs),
• Unilateral relief provisions,
• Inter-cantonal allocation and exemption-with-progression rules.

These mechanisms may not be “deductions” in the narrow sense, but they can reduce the share of income or tax attributable to Basel-Stadt.

Interaction Between Federal and Cantonal Deductions

Many expenses are relevant at both federal and cantonal level, but:

• Federal and cantonal caps may differ,
• Certain deductions may exist only at one level,
• The same expense can be treated differently in the federal and cantonal calculations.

When completing the tax return, taxpayers must apply the correct rules separately in the federal and Basel-Stadt sections.

Documentation and Evidence

The ability to claim deductions in Basel-Stadt depends heavily on proper documentation. Taxpayers should keep:

• Salary certificates and pension contribution statements,
• Tickets and invoices for commuting and work-related expenses,
• Contracts and invoices for childcare, education and training,
• Insurance premium statements,
• Bank and mortgage statements,
• Receipts for significant medical or extraordinary expenses.

Practical Considerations

The overall effect of deductions in Basel-Stadt depends on:

• The type and level of income,
• The taxpayer’s family and housing situation,
• The availability and size of deductible expenses,
• The interaction between federal rules and cantonal practice.

To understand your specific tax position, this Deductions section should be read together with the pages on Rates, Filing Requirements, Special Rules and Examples in the Basel-Stadt income tax guide.