t0 Customer API

Read and submit accounting records for the entity your API key belongs to.

Authenticate every request with the X-Api-Key header. The key is the scope: it resolves to exactly one entity, and every route reads or writes that entity's records.

Reads are served from the accounting system of record and are eventually consistent: a record created in act can take up to one export cycle (nightly) to appear here; records submitted through this API are readable as soon as the search index catches up. Every list response carries as_of.

Amounts and currencyCode are always the record's own transaction currency. Keys under customFields that start with t0_ are reserved for act: a documented few are returned, the rest are internal, and submitting one is rejected.

Reads honour the entity's first month of books: a record is visible when its date is on or after the books start date. This applies to dimension records (Customer, Vendor) you submit as well as to transactions, so date submitted records on or after the books start if they are to be read back.