From the death of his father Richard Walter (about 1755/6), until 1781 he was engaged in a prosperous business as a coal merchant. He played a leading part in establishing a Coal Exchange in London; but shortly after 1781, when he began to occupy himself solely as an underwriter and became a member of Lloyds, he over-speculated and failed.
In 1782 he bought from one Henry Johnson a patent for a new method of printing from logotypes (i.e. founts of words or portions of words, instead of letters), and made some improvements to it. In 1784 he acquired an old printing office in Blackfriars, which formed the nucleus of the Printing-house Square of a later date, and established there his Logographic Office.
At first he only undertook the printing of books, but on 1 January 1785 he started a small newspaper called The Daily Universal Register, which on reaching its 940th number on 1 January 1788 was renamed The Times.
The printing business developed and prospered, but the newspaper at first had a somewhat chequered career. On 11 July 1789 Walter was convicted of libel on the Duke of York and was sentenced to a fine of £50, a year's imprisonment in Newgate, to stand in the pillory for an hour and to give surety for good behaviour for seven years; for further libels the fine was increased by £100 and the imprisonment by a second year. On 9 March 1791, however, he was freed and pardoned on the request of the Prince of Wales.
In 1799 he was again convicted for a technical libel, this time on Lord Cowper. He had then given up the management of the business to his eldest son, William, and had (1795) retired to Teddington, where he lived till his death. In 1759 he had married Frances Landen (died 1798), by whom he had six children. William Walter very soon gave up the duties he undertook in 1795, and in 1803 transferred the sole management of the business to his younger brother, John.