What a sale changes in the books

Saving an invoice debits the customer, credits sales income and VAT, takes the goods out of stock and, for a cash sale, records the receipt in the same step.

Accounting Concepts
3 min read
Updated October 20, 2026

For Accountant Owner or manager Sales clerk

One save, several effects

Saving a sales invoice is one transaction. Either everything below happens, or nothing does and the screen says why.

What happens when you save an invoice

Area	Change
Customer's account	The customer owes the invoice total, on the invoice date
Sales income	Each line's amount is booked to the sales ledger of its product, or the company's sales ledger
VAT	The VAT adjustment's ledger is credited with the VAT on the bill
Discounts	A discount is booked as a deduction in its own ledger, so the customer owes less
Stock	Each stocked product leaves its warehouse, unless the invoice was made from a goods delivery note (the note already took the goods out)
Receipt	A cash sale, or a payment taken on the invoice screen, also saves a receipt in the same step
Number	The next number of the series the invoice was started from
IRD	When your company has IRD on, the invoice is queued to be sent (see How bills reach the IRD, and what to check when one does not)

Choose the customer and add the products
Who
Sales clerk
Where
Sales Invoice > Add
What changes
Nothing is booked yet. The screen works out line amounts, adjustments and the total as you type.
Save
Who
Sales clerk
What changes
The screen checks dates, stock, credit and required fields. If anything fails, it names the problem and nothing is saved.
The invoice is final
What changes
It appears in the list with its number and status, can be printed, and a customer receipt can be made against it.

What the numbers are

Customer owes = the net amount of the invoice: products, plus VAT, minus discounts.
Sales income = the basic amount of the lines, before VAT and discounts. A product can have its own sales ledger, so one invoice can credit several income ledgers.
VAT and discounts follow the sales adjustments chosen on the invoice: see VAT, discounts and sales adjustments.
The invoice is not changed by what the customer pays. Payments are separate receipts against the same customer account: see What clears what in the customer's account.

Worked example: one invoice in the books

An invoice to ABC Traders has two lines: 10 chairs at 600 (6,000), a product that uses the company's sales ledger, and one table at 4,000, a product with its own sales ledger, Furniture sales. There is a bill discount of 5%, ordered before VAT, and VAT at 13% (the rates set up for this example).

Working: products 10,000; discount 5% = −500, running total 9,500; VAT 13% of 9,500 = +1,235; invoice total 10,735.

Ledger	Debit	Credit
ABC Traders: what the customer owes	10,735
Company sales ledger: the chairs		6,000
Furniture sales: the table		4,000
Discount ledger	500
VAT ledger		1,235
Total	11,235	11,235

Sales income is the 10,000 before the discount and VAT; the discount is kept apart in its own ledger. In stock, 10 chairs and one table leave the warehouses of their lines.

Related guides

The books: ledgers, vouchers and the invoice Everything Penahak Accounting records is a numbered voucher that moves money between ledgers. The sales invoice is the voucher… Raise a sales invoice The invoice puts a sale into the books and takes the goods out of stock. Choose the customer, add the products, check the… VAT, discounts and sales adjustments VAT and discounts are sales adjustments. Each is a named rule with a rate, a sign, a ledger and an order, and the order decides… Cash sales and credit sales A cash sale is paid at once and leaves nothing owing. A credit sale is owed until the customer pays. The invoice screen chooses… What clears what in the customer's account A customer owes a balance; each invoice has its own due amount. A receipt clears an invoice only when it names that invoice. The… What IRD-ready means IRD-ready means invoices and credit notes carry what the IRD asks for and, when your company's IRD setting is on, are sent… Which documents move stock, and how A list of every document that changes stock: whether goods come in or go out, from which warehouse, at what value, and when (on… How stock is valued and what a sale costs Penahak values stock first in, first out (FIFO): the oldest goods are assumed to be sold first. The cost of a sale and the value…