CIS deduction errors?

Dcollins

Doing bookkeeping for a small subcontractor, and am getting frustrated with remittance advice notes from contractor. Some are OK, but others I don't understand.

This is an example from 2010:

Work done on site xxx £1409.80
Less contracharge invoice £164.50 (which included VAT at 17.5%)

I don't have a problem with the above, but the calculation quoted is:

Gross value £1,245.30
Less materials £0.00
Liable to deduction £1253.53
Tax deducted £250.71
Net payment £1002.82

There is no other financial information on the document. Am I missing something? The contractor is a large company, so should (we hope) be getting it right.
Where does £1,253.53 come from?

Any help welcome, thanks.

T.C.

It has got to be an error surely!?!

Dcollins

Got to be. Thanks. About a quarter of them are like this