The figure is more than twice the £5m that was estimated when Keydata was pushed into administration by the FSA in June.
At the end of July PwC said Keydata or Lifemark products invested with Lifemark S.A have been identified as non Isa eligible and therefore could incur tax liabilities.
It said income for these products, of which over £350m is invested, will be paid gross and clients will need to include all income paid by the administrators on their personal income tax return.
Meanwhile, PwC said it would pay income payments in gross on other suspended Keydata plans after it had satisfied itself that they were Isa eligible.
It said it would review all products that were sold through Isas in turn to determine their status in conjunction with the underlying product providers.
Schwarzmann says PwC failed to gain an indemnity from all the providers to process payments and has now agreed a procedure to satisfy itself that it can satisfy HMRC without incurring any tax liabilities.
He expects to have completed the review of 160 arrangements in September when income will flow for all investors.
He says: “Once we were clear what we needed from the Revenue, we went back to the product providers to request an indemnity so we could make income payments and all of them bar one said no.
“We have now agreed a procedure to satisfy ourselves that we can satisfy the Revenue and have started working through it.
“There’s about 160 to work through and we have already agreed now on over 20 to be processed.”