The `Invoice:` tag refers to an actual invoice, either generated by the

organization or received by the organization.  Typically, this is a document

that is a request for payment, rather than documenting an actual payment that

has occurred.  The value of the `Invoice:` tag is always a valid pathname in

repository to the document, [as described above](#documentation-tags).

Some examples of appropriate uses of the `Invoice:` tag are:

* an actual invoice as sent by a vendor to the organization.

* a request for payment sent by the organization to someone else.

* a reimbursement request submitted by an employee, contractor, or volunteer

  for expenses they've already incurred and would like the organization to

  reimburse (e.g., an expense report, requesting for reimbursement of travel

  expenses).

#### Statement Tag

The `Statement:` tag refers to any sort of written statement received from an

external party (or even perhaps generated internally) that provides document,

insight, or other information about the transaction.  The value of the

`Statement:` tag is always a valid pathname in the repository to the

document, [as described above](#documentation-tags).

Some examples of appropriate uses of the `Statement:` tag are:

* bank statements, as received from the banking institution.

* written reports of travel.

* blog posts made by a contractor documenting their work.

* written organizational policies about the expense.

* just about anything that is clearly not an [invoice](#invoice-tag) nor a

  [receipt](#receipt-tag), but definitely is valid backup documentation for

  the transaction.

#### TaxReporting Tag

The `TaxReporting` tag is an optional tag for `Assets` accounts that debit to

the account.

When provided, the `TaxReporting` accompanies a `TaxImplication` information

tag.  The TaxReporting refers to a document that verifies the choice for the

`TaxImplication` tag.  For example, for individual contractors in the USA, a

links to a [W-9](https://www.irs.gov/pub/irs-pdf/fw9.pdf) for the individual

being paid.  For a individual foreign contractor, the `TaxReporting` might

link to a

[W8-BEN](https://www.irs.gov/uac/form-w-8ben-certificate-of-foreign-status-of-beneficial-owner-for-united-states-tax-withholding)

for the payee.

### Information Tags

In contrast to documentation tags, information tags can more traditionally be

considered pure "meta-data" for a ledger entry.

#### Entity Tag

The `Entity:` tag is required for many types of ledger entries.  The value of

the `Entity:` tag is a unique moniker that identifies the organization,

company, person, or legal entity that is the external party for the

transaction.

Note that there is no database of these monikers, so typos can cause

trouble.  However, you could implement checks in

`accounts/config/config-tags.ledger` using a regular expression to verify no

typos have occurred.  This would be somewhat cumbersome, since Ledger CLI

would likely require that the monikers be encoded into a regular expression.

Barring that, the

[integrity of your data should be periodically checked](checking-integrity-of-tag).

#### IncomeType Tag

The `IncomeType:` tag is used for all `Income:` accounts.  This refers to the

type of income.  The value of the `IncomeType:` tag is always a string.

Since this particular system is designed for USA non-profit entities who file

USA Form 990, the following `IncomeType` values are supported:

* `Donations`, which refers to standard charitable donations.

* `RBI`, which refers to "related business income".

* `UBTI`, which refers to "unrelated business taxable income.

Not that donor-advised funds and government grants don't currently have their

own `IncomeType`.  It's possible this might be necessary; the authors aren't

familiar with how to handle those items on the Form 990.  It would be a

relatively simple change to `config-tags.ledger`, though, to support other

income types, or to change it entirely to handle use-cases other than USA

Form 990 filing.

#### TaxImplication Tag