Income tax audits can be done by Tax Centres (TC) and Tax Service Offices (TSO). TC conducts some very limited reviews of the tax returns filed, such as pre-assessment review of donations and tuition fees, post-assessment review of medical expenses and moving expenses. Most audits are conducted by auditors working in TSO. Auditors working in office audit program normally restrict their audit to business expenses reviews. They conduct their audit by correspondence and do not visit a business in the field. Auditors working the SME (Small and Medium Enterprises), Basic File, and Large File programs conduct their audits in the field, typically at the taxpayer's place of business. The audit conducted by field auditors are not restricted and could cover many and any issues in a tax return.