BulgariaA tax agreements and international conventions Special regimes for frontier workers are included in the following double taxation conventions: when a resident resident in Poland is in a foreign country which has not concluded a DTT with Poland, double taxation is avoided according to the imputation method. The taxable person established in Poland is responsible for the income tax levied on his world income, but this tax is proportionally reduced by the income tax paid abroad. Many SDRs have the same method of credit. However, some of them provide for the exemption method (i.e. foreign income covered by such an agreement is exempt in Poland). The Double Taxation Convention entered into force on 27 December 2006. .