One customer, Judith Ratcliffe, from Surrey, wanted to put her British Gas shares worth about pounds 2,000 into a single company PEP.
She sent off the shares by first class post on 8 March believing there was plenty of time before the 5 April deadline for the current tax year. There was no mention of a deadline on the bank's PEP form.
But NatWest had imposed a deadline of 11 March and said the application was delayed in the post and did not make the cut-off.
It did not write back to Mrs Ratcliffe until 17 March. The letter did not arrive until 22 March as the bank had sent it to the address on the share certificates despite the Ratcliffes' new address being pencilled in.
A NatWest spokesman said the bank decided to accept PEP trades up to 11 March because it could not guarantee that share certificates received after that would complete the procedure on time.
'We understand that Mrs Ratcliffe was disappointed,' he went on. 'The certificate was delayed in the post, but we shoud not have taken so long to respond.'
Alan Ratcliffe said all the documents were in his wife's name, yet the bank had written to Mr and Mrs Ratcliffe. 'PEPs are always in a single name,' he pointed out.
'I will be writing to NatWest and British Gas about the poor level of service.'
Midland Bank customers who want to put cash into a PEP will find that branches will accept it until Monday, but the bank will not guarantee that the PEP will be completed by the deadline.
Only arrangements made before yesterday were guaranteed to complete the procedure by the end of the tax year.Reuse content