A guarantor is someone who agrees to repay a loan if the borrower defaults. For loans between £500-£7500, a valid guarantor must be a UK homeowner aged 23-75 with a good credit history and income over £800/month. For £50-£500 loans, guarantors can be tenants or homeowners aged 18+. Common guarantors include family, friends, colleagues, or landlords. Borrowers apply online and loans may be approved within 24 hours.