Client - MTD Losses
A client's losses and loss claims under MTD Income Tax, across HMRC's two shapes. Up to 2025-26 a loss and a claim are each a record with an identifier — created once, amended through that id, deleted, and for carry-sideways claims ordered against each other. From 2026-27 the whole position is one set of figures per income source per year, replaced in full on every save. The amends are POST rather than PUT, mirroring HMRC, who refuse an amend that changes nothing.
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GET Get LossesReturns the losses and loss claims HMRC hold for the tax year, in whichever of their two shapes that year uses — isRecordBased says which. Empty lists.../tenants/{tenant}/clients/{client}/mtd/losses/{taxYear}
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POST Create Brought Forward LossRecords a loss carried forward from a year before Making Tax Digital and returns HMRC's identifier for it. Tax years to 2025-26 only. Not safe to repe.../tenants/{tenant}/clients/{client}/mtd/losses/brought-forward/{taxYear}
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POST Amend Brought Forward LossChanges a brought forward loss's amount — the only part HMRC let you change — and returns the loss as they now hold it. A POST rather than a PUT becau.../tenants/{tenant}/clients/{client}/mtd/losses/brought-forward/{lossId}/{taxYear}/amount
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DELETE Delete Brought Forward LossDeletes a brought forward loss. HMRC block this once the loss has been used in a final declaration — the way to take the figure out of the computation.../tenants/{tenant}/clients/{client}/mtd/losses/brought-forward/{lossId}/{taxYear}
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POST Create Loss ClaimClaims a loss and returns HMRC's identifier for the claim. Tax years to 2025-26 only, and HMRC accept nothing until the income source's accounting per.../tenants/{tenant}/clients/{client}/mtd/losses/claims
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POST Amend Loss Claim TypeChanges a loss claim's type — the only part of a claim HMRC let you amend — and returns the claim as they now hold it. A POST for the same reason as t.../tenants/{tenant}/clients/{client}/mtd/losses/claims/{claimId}/{taxYear}/type
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DELETE Delete Loss ClaimDeletes a loss claim. Who deleted it is recorded./tenants/{tenant}/clients/{client}/mtd/losses/claims/{claimId}/{taxYear}
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PUT Amend Loss Claims OrderReplaces the order in which HMRC apply the year's carry-sideways loss claims. A full replacement: every carry-sideways claim for the year must be in t.../tenants/{tenant}/clients/{client}/mtd/losses/claims/{taxYear}/order
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PUT Save Losses And ClaimsSends one income source's whole losses-and-claims position for a tax year from 2026-27 onwards. A full replacement of what HMRC hold — anything omitte.../tenants/{tenant}/clients/{client}/mtd/losses/document/{businessId}/{taxYear}
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DELETE Delete Losses And ClaimsClears the losses and claims HMRC hold for one income source and tax year (2026-27 onwards). Clearing is a delete rather than an empty save. Who delet.../tenants/{tenant}/clients/{client}/mtd/losses/document/{businessId}/{taxYear}