Text steganography uses text files as carrier files to hide confidential information. The goal of text steganography is to make the hidden data undetectable except the sender and receiver. This paper focuses on semantic-based text steganography. It hides confidential information by replacing words with their synonyms (same meanings). In international trading processes, products are imported and exported between foreign countries, in this case, the sellers and the buyers do not know each other. Therefore, the seller has a number of risks such as credit risk and legal risk caused by the distance. Letter of credit (LC) has been used to solve these risks. In the modern age, LC information has been sent online. Therefore, the security of LC information has become an important role. Most of the bank’s LC information is sent via SWIFT message, email or message formats. Using these types of message does not secure the LC information. This paper implements synonym substitution based algorithm to make confidential LC information more secure. This system is implemented by using Java software development kit (J2SE 7).