Why do companies prefer to use outside vendors rather than prepare iXBRL documents in-house?

The first reaction of most companies is to try and prepare the iXBRL statements in house using an accounts preparation software or an accounting software. This is probably easy if your financial statements are simple in structure and have a predictable set of notes to explain the numbers. A one time investment in the software and a limited investment of time and money in acquiring the know how should help a company in managing its obligations to HMRC in filing financial statements accompanying a corporate tax return in iXBRL format.