The tax period is the calendar year.
The basic filing and payment deadline is 1 April of the year following the tax period. As of 2021, an automatic extension to 1 May is possible for taxpayers filing electronically. The deadline of 1 July applies if a Czech registered tax advisor files the tax return, as long as a power of attorney authorising the registered tax advisor to prepare the return is filed by this deadline (i.e. before or together with the tax return at the latest). Further extension might be granted by the Czech tax authorities upon properly substantiated request. The same deadlines also apply to the payment of any outstanding annual tax liability (i.e. for taxpayers filing personally, it is 1 April or 1 May depending on the filing form; for tax advisors filing on behalf of taxpayers, it is either 1 April or 1 July). The deadline for tax refund is 30 days following the tax filing deadline (as detailed above) provided that the tax authorities approve the tax return.
Payment of tax
Income tax is withheld monthly at source from income from employment for employees of a Czech company or branch and for employees of a foreign company assigned to work in the Czech branch of that foreign company. Czech law also contains a deemed employer rule whereby an employee of a foreign company who performs work for, and takes orders from, a Czech individual or company may be seen as an employee for payroll withholding purposes irrespective of the legal employment arrangements. Unless the relevant DTT provides otherwise, non-resident individuals working in the Czech Republic (e.g. consultants) who are not employees will be subject to 15% withholding by the Czech entity/person paying for the services.
For all sources of income that have not been liable to Czech tax at source, individuals are responsible for making payments of tax in advance on the basis of prior-year liability. This usually applies to the employment income of foreigners assigned to the Czech Republic by an employer, regardless of whether the employer has a PE in the Czech Republic.