Social Investment Tax Relief (SITR) is a tax relief program in the United Kingdom that encourages individuals to make investments in certain types of social enterprises and organizations. The purpose of the program is to help these organizations access the capital they need to grow and have a positive impact on society.

Under SITR, individuals who invest in qualifying organizations can receive tax relief on their investments. The specific details of the relief vary depending on the type of investment and the organization, but in general, investors can receive a reduction in the amount of income tax or capital gains tax they owe.

To be eligible for SITR, an organization must be a "qualifying organization." This includes a wide range of social enterprises, such as community benefit societies, community interest companies, and charitable organizations, as well as certain types of community-focused organizations such as co-operatives, community benefit partnerships, and credit unions. Investment must be made in the form of a loan, or share purchase and the minimum investment requirement is 100 Pounds

It's worth noting that there are limits on the amount of investment that can qualify for SITR and certain restrictions on who can invest and receive the relief. Therefore, it is important to consult a tax professional or the UK government's guidance before making an investment in order to understand the specific details of the relief, and if it applies to your individual situation.