A payment is money that actually moved. Don't confuse it with a due amount, which is a sum that is expected but not yet paid. For a payment to move the balance correctly, it must then be reconciled with the due amount(s) it covers.
Here's how to proceed:
Open the relevant contract and click the Financials tab.
In the Financial transactions section, click + Add a transaction.
In the New transaction window, click Payment (the other choices are Due amount, Discount and Free rent/charges period), then click Next.
Under Direction, choose the direction of the payment:
Incoming payment (Tenant → Owner): money the tenant paid you.
Outgoing payment (Owner → Tenant): money you pay the tenant, for example a reimbursement.
In Amount, enter the amount received or paid.
In Date, enter the date of the payment.
Select the Payment method from the dropdown.
If needed, add a Description (optional).
Click Save.
Reconciling the payment
After saving, the Reconciliation screen opens. At the top, the payment and its To match amount are shown. Below, under Due amounts and refunds awaiting matching, tick the due amount(s) that correspond to this payment. The To match amount decreases with each box you tick; the goal is to bring it down to 0,00 €. A payment can cover several due amounts, or only part of one. Then click Save to confirm.