A simple annuity is an annuity where the payment interval is the same as the interest period. Examples of annuities include regular savings deposits and monthly mortgage or insurance payments. Annuities can also be classified as ordinary or due depending on whether payments are made at the end or beginning of each period, and as certain or contingent depending on whether payments are made over a definite or indefinite time period. Grade 11 will focus on ordinary annuities where payments are made at the end of each period and annuities certain where payments are made over a definite time period.