By Marcela Ayres

BRASILIA, May 31 (Reuters) - Brazil's government expects to raise tax revenue by 13 billion reais ($4 billion) this year with a new tax refinancing plan created by decree on Wednesday, a source with knowledge of the matter said.

A previous tax refinancing plan that expired on Wednesday had tougher rules and the government estimated it would raise an additional 8 billion reais.

The new refinancing program allows taxpayers to have discounts on fines and interest charges that were not allowed by the previous program, the source added, asking for anonymity to discuss the matter freely.

Taxpayers who joined the previous tax refinancing program are allowed to adhere to the new one, the source said.

Companies and individuals will be allowed to pay tax debts in up to 15 years. If shorter payment periods are chosen, taxpayers may have up to 90 percent cut on interest charges and 50 percent on fines. Brazil Finance Minister Henrique Meirelles said earlier on Wednesday the new tax refinancing program may have a future negative effect on tax revenue but only by 2019. ($1 = 3.2262 reais) (Writing by Tatiana Bautzer; Editing by Bill Trott)