API accounting periods, allocations and dry runs

Dates, allocations and dry runs

Accounts dates and Corporation Tax coverage are separate. Supply first_return_end when the first return has a non-default boundary. In enter-once mode, customer-entered capital, donation, dividend, waiver and CT600E allocations carry the two dated returns. Allocation suggestions are informational and are never applied to a live filing. In separate-figures mode, send entered_returns with each company return's own figures. Clubs use their existing enter-once route.

Box 205 other income and its Other income not taxable adjustment retain the existing day allocation. A one-off receipt in that category can consequently appear in both returns. See long first accounting periods and filing only the remaining CT600.

Set dry_run to true to validate and prepare documents without submission or a live filing slot. Missing answers return state incomplete, fields, suggested_allocations and an empty previews array. Complete requests return a filing operation to poll while documents are generated. A completed dry run reports complete or incomplete. We retry a dry run automatically after a temporary execution failure, up to three attempts. Preview downloads contain draft documents only. Never treat a partial preview as filing ready.

Uploaded charity or club accounts are acquired separately: POST /uploads/accounts, upload the returned signed object, then PUT /uploads/accounts to finalise and verify it. Put the returned immutable accountsFile into the existing accounts file field. Use the documented upload shape in the generated contract.