Invoicing

Businesses send invoices to clients to request payment. You may want to track, eg:

how much is due to be invoiced
how much has been invoiced but not yet paid
how much has been invoiced and paid.

How to record invoices and payments varies depending on whether the business uses the Accrual or Cash accounting method.

Accrual accounting

Revenue is recorded (and taxed) in the period when the corresponding goods/services are provided - not at the time of payment, which usually happens after some delay. The expected payment is tracked as a receivable, which is a type of asset.

A good time to record revenue is when the receivable is created (by sending the invoice). So:

2020-02-01 * (202001ab) AB Inc. | invoice for work done in january
    revenues:consulting:ab     $-1000
    assets:receivable:ab        $1000

2020-02-15 * AB Inc. | receive full payment for 202001ab
    assets:receivable:ab       $-1000 ;= $0  ; optional: when paid in full, assert that
    assets:checking             $1000

Cash accounting

Revenue is recorded when money is actually received:

2020-02-15 * AB Inc. | receive full payment
    revenues:consulting:ab     $-1000
    assets:checking             $1000

Tracking invoices with cash accounting

Invoices are strictly speaking not part of cash accounting. But if you want to track them, you could use equity to balance the transactions, as follows:

2020-02-01 * (202001ab) AB Inc. | invoice for work done in january
    assets:receivable:ab        $1000
    equity:receivable          $-1000

2020-02-15 * AB Inc. | receive full payment for 202001ab
    equity:receivable           $1000
    assets:receivable:ab       $-1000 = $0
    revenues:consulting:ab     $-1000
    assets:checking             $1000

Or use unbalanced postings (use a special top level account to avoid unbalancing the accounting equation, if you care about that):

2020-02-01 * AB Inc. | invoice for work done in january
    (invoices:receivable:ab:202001ab)        $1000

2020-02-15 * AB Inc. | receive full payment for 202001ab
    (invoices:receivable:ab:202001ab)  $-1000 = $0
    revenues:consulting:ab             $-1000
    assets:checking                     $1000

Estimated tax

If you're a freelancer in the US, eg, you may be responsible for paying estimated income taxes. Here's the above transaction, with additional postings to track and save for tax owed:

2020-02-15 * AB Inc. | receive full payment for 202001ab and save estimated tax
    equity:receivable           $1000
    assets:receivable:ab       $-1000 ;= $0
    revenues:consulting:ab     $-1000
    equity:payable:us:2020       $150  ; estimate new tax owed, eg 15% 
    liabilities:tax:us:2020     $-150
    assets:checking:tax:us:2020  $150  ; save that amount (in a virtual subaccount)
    assets:checking              $850

Cash accounting, invoices, reimbursed expenses, and estimated tax

Another example:

2025-11-10 * AB Inc. | some expense
    assets:bank:wf:bchecking                 $-50
    assets:receivable:ab:202511ab             $50

2025-11-14 * AB Inc. | another expense
    assets:bank:wf:bchecking                 $-40
    assets:receivable:ab:202511ab             $40

2025-12-05 * AB Inc. | invoice
    equity:unrecognisedrevenue             $-1000
    assets:receivable:ab:202511ab           $1000
    ; + $90 reimbursements, already recorded

2025-12-12 * AB Inc. | payment for 202511ab invoiced on 2025-12-05
    ; receive payment
    assets:receivable:ab:202511ab         $ -1090 = $0
    assets:bank:wf:bchecking               $ 1090
    ; recognise revenue
    revenues:ab                           $ -1000
    equity:unrecognisedrevenue             $ 1000 = $0
    ; estimate income tax
    liabilities:tax:2025:us                $ -250  ; 25% of revenue (eg)
    expenses:tax:2025:us                    $ 250
    liabilities:tax:2025:hi                 $ -60  ;  6% of revenue (eg)
    expenses:tax:2025:hi                     $ 60