Introduction

There functionality of Deposit Accounts covers typical use-cases of deposit account in microfinance which are Fixed-Term Deposits and Certificate of deposit.

Fixed-Term Deposit (FD): is money deposited at bank/mfi that cannot be withdraw for a specified term/tenure (unless a penalty is paid). When the term is over it can be withdrawn or it can be held for another term.
Certificate of Deposit (CD): Certificate deposit is different from that of fixed-term deposit in terms of its negotiability. CD is negotiable and can be rediscounted when the holder needs some liquidity, while fixed deposit must be kept until maturity.

Creating/Opening a Deposit Account

When opening/creating a deposit account the following details need to be known:

Term/tenure: What is the length of the term/tenure (in months)
Deposit amount: How much money is being deposited for the term. There would typically be some rules around min and max deposit supported.
Nominal annual interest rate: What is the interest rate to be applied to deposit amount for the term expressed as a nominal annual rate. There would typically be some rules around min and max interest rate supported.
Interest compounding frequency: Interest is usually compounded at periodic intervals like monthly, quarterly, annually
Commencement date: On what date does the term/tenure commence from.

Using the above information, it should be possible to derive the following at time of opening/creating a deposit account:

Maturity date: Given commencement date and tenure lenth, maturity date is known.
Accrued interest on maturity: Given the deposit does last until maturity date as intended, the amount of interest accrued on the deposit over the term can be calculate using algorithm
Maturity amount: Given the deposit does last until maturity date as intended, this is simply the sum of origin deposit amount and the accrued interest on maturity.

Renewing a Deposit Account

Its typically to allow a customer to renew an existing deposit account on maturity.